LIB  RARY 

OF  THE 

UNIVERSITY  OF  CALIFORNIA 

GIKT    OK 


4- 

OCT 


Jb 


Received     -OCT.  271892---,  189 

Accessions  No.  .U£&<£$3L      Shelf  No.  . 


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OUTLINES 


OP 


COMPARATIVE  ANATOMY 


AND 


MEDICAL    ZOOLOGY. 


HARRISON   ALLEN,  M.D., 

PROFESSOR  OF  ZOOLOGY  AND  COMPARATIVE  ANATOMY  IN  THE  UNIVERSITY  OF   PENNSYLVANIA. 


PHILADELPHIA: 
J.    B.    LIPPI^COTT     &     CO. 

1869. 


Entered,  according  to  the  Act  of  Congress,  in  the  year  1868,  by 
HARRISON    ALLEN,   M.D., 

In  the  Clerk's  Office  of  the  District  Court  of  the  United  States  in  and  for  the  Eastern 
District  of  Pennsylvania. 


TJHIVBRS1T7 


PREFATORY  NOTE. 


IN  the  spring  of  1866,  a  desire  was  expressed  by  the  Class  to 
have  the  author's  Lectures  on  Comparative  Anatomy  and  Zoology 
published  for  distribution.  Nothing  definite,  however,  was  determ- 
ined upon  until  the  following  spring,  when  arrangements  were  en- 
tered into  which  have  resulted  in  the  appearance  of  this  little 
volume.  It  is  in  many  respects  somewhat  fuller  than  a  synopsis, 
'which,  however,  in  general  features,  it  resembles.  Although  pre- 
pared in  answer  to  the  expressed  needs  of  a  class  composed  chiefly 
of  Medical  Students,  it  is  hoped  that  it  may  not  be  without  value  to 
the  cultivators  of  rational  anatomy  elsewhere. 

In  the  attempt,  apparent  in  different  portions  of  the  book,  to  frame 
general  definitions  and  give  brief  classifications  of  anatomical  sys- 
tems, the  author  is  fully  aware  of  the  liability  to  error  thus  incurred. 
Any  conclusions  based  upon  the  present  state  of  a  science  so  ac- 
tively cultivated  as  Comparative  Anatomy  may  eventually  prove 
of  but  doubtful  utility.  It  is  easy  to  group  about  assumed  stand- 
points the  observations  of  others,  but  more  difficult  to  preserve  in 
such  arrangements  harmony  between  the  old  and  new  facts.  In 

(iii) 


IV  PREFATORY   NOTE. 

proposing  such,  the  author  has  been  actuated  by  a  sincere  desire  to 
simplify  a  confessedly  intricate  subject. 

In  conclusion,  he  would  desire  to  express  his  acknowledgments  to 
Dr.  George  H.  Horn  for  the  contribution  of  the  articles  on  Hemip- 
tera  and  Cantharis ;  as  well  as  to  Professors  Joseph  Leidy,  Ed- 
ward D.  Cope,  and  Horatio  C.  Wood,  Jr.,  for  assistance  rendered 
while  the  work  was  passing  through  the  press. 


CONTENTS. 


OOMPAEATIVE  ANATOMY. 

PAGE 

PREFATORY  NOTE 5 

I.  Introduction 9 

Elements  of  structure 9 

Organism 10 

Distinctions  between  vegetables  and  animals 11 

Division  of  functional  labor 12 

II.  Classification 13 

Plan  of  star 15 

^              Sac 17 

Ring 19 

Vertebra .'.,  20 

III.  Skeleton ; 23 

Nature  of  limbs  in  Vertebrata 31 

Table  of  elements  of  cranial  vertebrae 34 

IV.  Articulation 35 

V.  Apparatus  of  motion 36 

VI.  Teeth 38 

VII.  Digestive  system 44 

VIII.  Circulatory  and  respiratory  systems 52 

Swim  bladder 60 

Relation  of  branchial  arches  to  stylo-hyoid  ligament 61 

Spleen 63 

Lymphatics 64 

IX.  Excretory  system 64 

Kidney 65 

X.  Integument 68 

XI.  Nervous  system 72 

XII.  Animal  electricity  and  phosphorescence 82 

Torpedo 82 

Gymnotus. 83 

Malapterurus 84 

Animal  phosphorescence 86 

(v) 


VI  CONTENTS. 

PAGE 

XIII.  Special  organs 87 

Lasso  cells 88 

Organs  of  touch 88 

Organs  of  smelling 91 

Eye 92 

Appendages  to  the  eye 95 

Ear 96 

XIV.  Sexual  characters 101 

XV.  Reproductive  system 103 

Sperm  cell 103 

Ovum 104 

Organs  of  generation 109 

Testicle 109 

Ovary 109 

XVI.  Generation 120 

Mammary  gland 135 


MEDICAL  ZOOLOGY, 

Mammalia 137 

Moschus 137 

Viverra 139 

Castor 139 

Hyrax 141 

Catodon 142 

Reptilia 143 

Caudisona ... 143 

Crotalus 143 

Ancistrodon 144 

Vipera 144 

Cerastes 144 

Naja 144 

Hydrophis 145 

Pisces 145 

Gadus 145 

Acipenser 145 

Insecta 147 

Cantharis 147 

Acanthia 151 

Notonecta 152 

Nepa 153 

Aphis , 153 

Coccus 153 

Apis t 154 

Cynips 155 


CONTENTS.  Vll 

PAGE 

Pulex 156 

Pediculus 156 

Arachnida 157 

Sarcoptes 157 

Demodex 158 

Myriapoda 159 

Scolopendra 159 

Annelida 159 

Hirudo : 159 

Entozoa 161 

Nematoidea 161 

Trichina 161 

Strongylus 162 

Trichocephalus 162 

Ascaris 163 

Oxyuris 164 

Sclerostoma 164 

Dracunculus 164 

Eustrongylus 165 

Trematoda 165 

Fasciola 165 

Distoma 166 

Bilharzia 167 

Tetrastoma 168 

Hexathyridium 168 

Development  of  trematoda 168 

Cestoda 169 

Taonia 169 

Bothriocephalus 171 

Development  of  Cestoda 172 

Mollusca 174 

Sepia 174 

Protozoa 174 

Infusoria 174 

Virgulina 174 

Vibrio 174 

Paramecium 175 

Cercomonas 175 

Trichomonas 175 

Psorospermise 175 

Gregarinidae 176 

Spongia 177 

Additions 178 

TABLE  or  CLASSIFICATION 179 

INDEX 185 


UH17BRSITT 


COMPARATIVE    ANATOMY. 


i. 

INTBODUOTIOff, 

ELEMENTS   OF   STKUCTURE. 

THE  composition  of  all  bodies  is  either  inorganic  or  organic. 

An  inorganic  (mineral)  body  is  homogeneous  in  structure, 
and  is  either  crystalline  or  without  definite  form.  Its  increase 
results  from  external  accumulation  of  particles.  An  organic 
body  is  a  product  of  organization.  An  organized  body 
(organism)  is  heterogeneous  in  structure,  and  has  a  definite 
form.  Its  increase  results  from  nutritive  processes  carried 
on  within. 

Every  organized  body  is  composed  of  ultimate  and  proxi- 
mate physical  elements. 

THE  ULTIMATE  PHYSICAL  ELEMENTS  are  (1)  homogeneous 
liquid, — as  in  the  germinative  area  of  the  egg  immediately 
after  impregnation ;  (2)  homogeneous  granules, — as  in  Monas 
crepusculum ;  (3)  homogeneous  filaments, — as  in  cilia,  sper- 
matic filaments,  and  Vibrio;  (4)  homogeneous  membrane, — 
as  in  basement  membrane.  (Leidy.) 

THE  PROXIMATE  PHYSICAL  ELEMENTS  result  through  union 
of  the  ultimate  elements.  They  are  very  constantly  pro- 
nounced in  varieties  of  the  organic  cell,  of  which  it  is  conve- 
nient to  speak,  as  an  early,  though  not  a  primordial,  expres- 
sion of  form. 

As  usually  described,  the  organic  cell  is  a  minute  form, 
composed  of  homogeneous  membrane  with  intervening 

(9) 


10  COMPARATIVE   ANATOMY. 

spaces  occupied  with  homogeneous  liquid.  Three  concen- 
tric spheres  can  commonly  be  detected :  the  first  (nucleolus) 
placed  within  the  second  (nucleus);  the  third  (cell  wall)  en. 
closing  the  other  two.  Homogeneous  granules  appear  within 
the  liquid,  and  filaments  (cilia)  may  be  appended  to  the  cell 
wall. 

FORMS  OF  CELLS  are  round,  oblong,  elongate,  cylindrical, 
compressed,  polygonal,  and  stellate.  Surrounding  conditions 
and  position  determine  shape. 

PROPERTIES  OF  CELLS. — In  addition  to  the  nutritive  pro- 
cesses common  to  all  organisms,  may  be  mentioned  fissura- 
tion  and  motility. 

Relations  of  cells  to  histogenesis  lead  to  consideration  of 
origin  and  significance  of  cells. 

1st  Theory. — Cells  originate  spontaneously  in  a  homoge- 
neous fluid,  in  the  form  of  granules  (nucleoli).  Around  these 
granules  are  subsequently  developed  others  assuming  the 
form  of  the  remaining  constituents  of  the  cell,  to  be  recog- 
nized as  the  nucleus  and  cell  wall.  (Schleiden  and  Schwann.) 

2d  Theory. — Omni  cellulce  e  cellula.  (Yirchow.) 

3d  Theory  (generally  known  as  the  germinal  theory). — The 
terminology  of  the  cell  is  discarded,  and  the  phrases  "ger- 
minal matter"  and  "formed  matter"  substituted.  The  former 
is  a  structureless  plastic  substance  everywhere  pervading 
organized  bodies,  to  which  the  formed  matter  stands  in  the 
relation  of  an  evolved  substance.  (Beale.) 

ORGANISM. 

All  organisms  are  sexual  beings,  and  are,  for  the  most 
part,  composed  of  cells. 

Many  inferior  organisms  assume  the  form  of  cells,  as 
Amoeba*  and  .Bodo.  The  ovum,  apparently  a  cell,  is  in  re- 
ality an  undeveloped  organism.  The  difference  between  a 

*  Amceba,  one  of  the  lowest  of  Ehizopoda, — composed  of  sarcode,  with 
an  outer  structureless  diaphanous  integument,  and  containing  an  interior 
circular  contractile  vesicle.  Measurement,  from  ^  to  -Z-^Q-Q"  long.  Is  found 
in  stagnant  water. 


INTRODUCTION.  11 

cell  and  an  organism  can  be  determined  only  by  tracing  out 
the  life-history  in  each. 

DISTINCTIONS    BETWEEN   VEGETABLES   AND   ANIMALS. 

Many  attempts  have  been  made  to  separate  vegetables  from 
animals.  The  cell  being  common  to  both  groups,  attempts 
have  been  made  to  separate  them  by  its  means.  A  sphere 
of  homogeneous  membrane  intervening  between  nucleus  and 
wall  of  the  vegetable  cell,  not  peculiar  to  it;  an  analogous 
membrane  is  seen  in  cartilage  cell. 

There  is  no  difficulty  in  separating  high  plant  froni  high 
animal,  as,  for  example,  a  horse  from  a  tree;  but  acknowl- 
edged difficulty  in  distinguishing  low  forms,  as  a  sponge 
from  a  Protococcus,  an  Amceba  from  an  (Ethalium.  But,  as  a 
rule,  confusion  obtains  not  so  much  among  the  very  lowest 
forms  of  animal  and  vegetable  life,  as,  for  example,  between 
Rhizopoda  and  Protophytse,  as  it  does  between  others  higher 
in  the  scale,  as  between  certain  Infusoria  and  Fungi,  as  the 
Myxomycetes. 

Linnaeus'  definition:  "Stones  grow;  plants  grow  and  live ; 
animals  grow,  live  and  feel." 

Objections. — Stones  do  not  grow,  but  increase  in  size  by 
accretion.  Feeling  may  be  said  to  exist  in  the  lower  classes  of 
both  plants  and  animals,  provided  that  contractility  be  accepted 
as  a  property  of  sensitive  tissue.  If  it  be  surmised  that  pain 
is  a  result  of  feeling  (i.  e.  sensation),  it  may  be  attributed  to 
(Ethalium  with  equal  propriety  as  to  Amceba.  Were  every 
act  of  fissuration,  evisceration  or  amputation  accompanied 
with  pain,  it  becomes  difficult  to  understand  why  self-mutila- 
tion should  be  so  frequently  imposed  for  the  preservation 
of  both  individual  life  and  that  of  the  species  (see  p.  120).  It 
is  probable  that  at  such  times  an  organism  feels  no  more 
pain  than  is  experienced  by  the  contractile  contents  of  an 
ovum  undergoing  segmentation. 

Among  the  attempts  which  have  been  made  to  separate 
plants  from  animals,  may  be  mentioned  the  following — 
placed,  for  convenience,  in  the  form  of  propositions  and  ob- 
jections: 


12  COMPARATIVE   ANATOMY. 

Prop.  1st.  That  while  plants  inspire  carbonic  acid  they 
expire  oxygen — the  process  being  reversed  in  animals.  Obj. 
Plants,  in  absence  of  sunlight,  or  in  times  of  flowering,  ex- 
hale carbonic  acid. 

Prop.  2d.  That  plants  do  not  possess  cilia — animals  do. 
Obj.  Many  zoospores  of  plants  are  ciliated.  Entire  groups  of 
animals,  as  higher  articulates  and  osseous  fishes,  are  without 
them. 

Prop.  3d.  That  plants  are  without  stomachs — all  animals 
possess  stomachs.  Obj.  The  amoeboid  stage  of  development 
of  (Ethalium  has  a  stomach  in  the  same  sense  as  Amoeba; 
while  Tcenia  (tapeworm)  is  without  a  stomach. 

Prop.  4th.  That  plants  have  cellulose  and  starch  as  chemi- 
cal constituents  of  tissue — animals  have  not.  Obj.  The 
mantle  of  the  Tunicata  contains  cellulose ;  the  ventricles  of 
human  brain  contain  starch  granules. 

Prop.  5th.  That  plants  are  stationary — while  animals  are 
contractile  and  motile.  Obj.  Many  plants  have  active  con- 
tractile zoospores,  and  Volvox  globator  and  the  Diatomaceae 
are  essentially  motile. 

We  cannot,  therefore,  well  express  the  difference  between 
a  plant  and  an  animal ;  but  can  only  ascertain  the  position  of 
each  disputed  form  by  contrasting  the  sum  of  its  life-phases 
with  that  of  acknowledged  types,  as  determined  by  develop- 
ment and  sexual  condition. 

Contrasts  between  animals  arise  from  the  variety  of 
methods  by  which  the  processes  of  life  are  performed.  In 
the  Amceba  these  processes  are  carried  on  in  a  common  tissue 
(sarcode),  so  that  at  different  times  the  same  structure  is  sub- 
servient to  different  uses.  But  among  the  higher  animals, 
which  have  many  tissues,  each  organ  has  a  limited  functional 
power ;  the  degree  of  such  limitation  bearing  a  fixed  relation 
to  the  multiplicity  of  organs,  so  that  in  the  highest  animals 
each  organ  has  but  a  single  function  to  perform.  Indeed, 
every  animal,  it  is  thought,  has  its  tissues  so  specialized  that 
the  degree  of  its  specialization  is  expressive  of  its  position  in 
the  class  to  which  it  belongs. 


CLASSIFICATION.  13 

This  leads  to  the  following  law  : 

The  successive  degrees  of  development  attained  by  the 
animal  kingdom  depend  upon  the  extent  to  which  functional 
labor  is  divided. 


II. 

CLASSIFICATION, 

CLASSIFICATION  is  the  arrangement  of  objects  into  groups, 
the  limitations  of  which  are  determined  by  some  precon- 
ceived standard  of  comparison. 

Classifications  are  artificial  or  natural,  as  the  standard 
chosen  is  either  false  or  true.  Thus  the  classification  of  ani- 
mals, according  to  Aristotle,  is  artificial,  since  the  standard 
assumed,  viz.,  the  coloration  of  the  blood,  is  false.  An  arti- 
ficial classification  is  the  result  of  an  imperfect  knowledge  of 
the  things  classified. 

It  is  only  by  an  intimate  acquaintance  with  the  anatomy, 
physiology,  and  development  of  each  animal,  that  we  can 
determine  in  what  tissues,  and  at  what  time,  the  true  stand- 
ard for  comparison  exists.  As  a  rule,  the  hard  tissues,  such 
as  the  shell,  bone,  teeth,  scales,  etc.,  furnish  excellent  second- 
ary characters;  yet  in  sub-groups  of  Vertebrata,  soft  tissues, 
as  the  blood  and  brain,  afford  reliable  data.  Sexual  char- 
acters are  occasionally  of  value,  as  the  mammary  gland,  in 
Mammalia,  and,  in  a  less  degree,  the  construction  of  the 
penis  in  the  same  class.  The  male,  in  Vertebrata,  conveys 
the  expression  of  potentiality  of  species;  in  lower  types,  it  is 
subordinate. 

Maturity  very  generally  yields  the  true  standard  of  com- 
parison. Yet  examples  are  not  rare  where  it  is  best  seen  in 
the  young.  The  articulated  condition  of  Lepas  (barnacle)  is 
noticed  only  in  the  larval  stage  of  the  animal.  The  chorda 
dorsalis — the  distinctive  feature  of  the  Vertebrata — disap- 
pears (in  comparatively  few  instances  only  is  it  persistent, 
viz.,  Cartilaginous  fishes)  before  birth. 


14  COMPARATIVE  ANATOMY. 

The  early  condition  of  the  embryo  itself  may  determine 
the  position  of  the  animal.  Thus  in  contrasting  the  early 
stage  of  the  developing  egg  of  an  articulate  with  that  of  a 
vertebrate  animal,  it  can  be  ascertained  before  the  appear- 
ance of  rings  on  one  hand,  or  chorda  dorsalis  on  the  other, 
to  which  type  the  animal  belongs.  In  the  first,  the  embryo 
presents  serrated  borders,  and  is  without  a  median  groove; 
in  the  second,  there  is  a  median  grove,  but  no  lateral  ser- 
rations. 

Apart  from  the  application  of  the  general  law  (p.  1 3),  the 
inferiority  of  an  animal  within  its  group  can  be  determined 
either  (1)  by  the  repetition  of  parts,  or  (2)  by  the  permanency 
of  embryonic  conditions.  (1)  The  tentacles  and  partitions  of 
Actinia  are  indefinitely  repeated  throughout  life;  they  are 
reduced  to  a  fixed  number — eight — in  Alcyonium:  therefore 
Actinia  is  a  lower  form  of  polyp  than  Alcyonium.  In  like 
manner  Gammarus  (fresh-water  shrimp),  a  crustacean  articu- 
late, from  the  repetition  of  its  segments,  is  a  type  inferior 
to  Lupa  dicantha  (crab),  where  they  are  consolidated  toward 
the  anterior  extremity  of  the  animal.  (2)  "Upon  observing 
among  acaleph  radiates  that  the  genus  Hydra  corresponds 
in  form  to  the  first  larval  change  of  the  Amelia  (see  p.  126), 
Hydra  is  said  to  be  a  lower  form  than  Amelia.  In  perceiving 
that  a  canal  of  communication  between  an  arterial  and  venous 
current  (foramen  of  Botal)  obtains  in  the  systemic  circulation 
of  the  reptile,  while  such  a  condition  is  peculiar  to  the  foetal 
circulation  of  the  mammal,  the  reptilian  type  is  said  to  be 
lower  than  the  mammalian. 

When  the  relations  of  closely  allied  animals  are  sought 
for,  the  characters  are  selected  not  so  much  from  their  phy- 
siological importance  as  from  their  constancy.  Indeed,  the 
most  important  vital  organs  with  some  groups  of  animals 
may  furnish  no  characters  for  classification — as,  for  example, 
the  heart  in  insects;  while  others  having  no  apparent  sig- 
nificance, such  as  minute  differences  in  form  and  number  of 
joints  of  antennse,  may  be  of  the  greatest  value. 

Systems  of  classification  change  with  increase  of  knowl- 
edge, and,  all  things  being  equal,  the  latest  is  the  best.  But 


CLASSIFICATION.  15 

it  appears  probable  that  the  present  classification  will  never 
be  materially  altered.  The  main  features  are  for  the  most 
part  defined  with  clearness.  As  a  result,  a  number  of  plans 
or  types  of  structure  are  seen  in  the  animal  kingdom — each 
plan  or  type  being  taken  as  the  standard  of  comparison  for 
all  animals  included  within  its  limits.  To  these  ideal  pat- 
terns the  tissues  more  or  less  regularly  conform.  If  they 
have  the  significance  by  many  attributed  to  them,  namely, 
in  each  being  the  expression  of  a  divine  idea,  it  follows  that 
the  great  principles  of  classification  are  fixed. 

These  plans  are  four  in  number,  and  are  arranged  in  ac- 
cordance with  the  capacity  possessed  by  each  for  develop- 
ment, as  follows: 

STAR.  SAC.  RING.  VERTEBRA. 

In  that  large  group,  the  Protozoa,*  no  plan  or  plans  have 
yet  with  certainty  been  recognized. 

STAR  (Radiata). 

A  radiate  animal  is  one  having  its  parts  disposed  around 
a  common  central  axis,  and  diverging  from  it  to  the  periph- 
ery. (Agassiz.) 

Divided  into  groups  of  Coelenterata  and  Echinodermata. 

Coelenterata  subdivided  into  Polypi  and  Acalephee. 

*  PROTOZOA.  This  term  was  proposed  by  Siebold  to  designate  a  group  of 
animals,  characterized  by  the  various  systems  of  organs  not  being  distinctly 
separated.  (Griffith  in  Micrograph.  Diet.) 

Divided  into  Rhizopoda,  Spongida,  and  Infusoria. 

Rhizopoda. — Essential  characters  are  the  gelatinous  composition  of  the 
body,  and  the  locomotive  organs  consisting  of  variable  foot-like  processes 
(pseudo-podia).  (Griffith,  ibid.) 

Spongida. — Fixed,  aquatic,  polymorphous  animals;  inhaling-and  imbibing 
the  surrounding  element  through  numerous  contractile  pores  situated  on 
the  external  surface ;  conveying  it  through  internal  canals  or  cavities,  and 
ejecting  it  through  appropriate  orifices ;  having  an  internal  flexible  or  in- 
flexible skeleton.  (Bowerbank.) 

Interior  mass  occupied  with  numbers  of  chambers  lined  with  flagellate 
cell-like  bodies.  (Carter.) 

Infusoria. — Form  variable,  fixed  or  free,  round,  oval,  etc.,  with  integument 
furnished  either  with  a  ciliated  spiral  line,  or  a  single  flagellum.  Interior 
mas's  slightly  specialized;  a  gullet  and  contractile  vesicles  making  their 
appearance. 


16  COMPARATIVE   ANATOMY. 

Polypi. —  Composed  of  a  sac  divided  into  chambers  by 
partitions  arranged  to  the  periphery  (integument),  as  radii 
to  a  central  point — the  stomach.  Such  partitions  may  be 
more,  though  never  less  than  six  in  number.  "The  upper 
margin  of  body  is  fringed  by  hollow  tentacles,  each  of  which 
opens  into  one  of  the  chambers."  They  may  be  naked  and 
present  indefinite  numbers  of  partitions  and  tentacles,  as  in 
A ctinia  (sea-anemone);  or  possess  a  definite  yet  large  number 
of  tentacles  often  accompanied  with  depositions  of  calcareous 
matter  within  walls  between  partitions,  as  in  Madrepora 
(coral);  or  the  tentacles  may  be  restricted  to  six,  with  a  tend- 
ency to  formation  of  calcareous  skeleton,  as  in  Alcyonium. 

Acalephse. — This  is  a  numerous  and  diversified  group,  com- 
posed for  the  most  part  of  individuals,  which,  when  mature, 
have  a  dome  or  umbrella-like  form.  The  organs  and  systems 
of  vessels  are  arranged  in  a  stellate  manner  to  a  central  point. 
Divided  into  Ctenophorse,  Discophorse,  and  Hydroida. 

Acalephs  move  by  means  of  minute  flappers  arranged  in 
vertical  comb-like  rows  on  outer  side  of  the  dome-like  struc- 
ture, as  in  Ctenophorse;  or  through  the  movements  of  the 
edges  or  general  contractile  power  of  the  Discophorse  and 
Hydroida. 

In  the  last  two  groups,  remarkable  features  are  seen  in  the 
development  of  the  young,  the  larval  condition,  as  a  rule, 
remaining  fixed  and  dissimilar  in  form  to  the  adult.  (See 
p.  124.) 

Echinodermata.  —  This  is  the  highest  group  of  radiates, 
composed  of  stellate  globular  or  oblong  forms,  rarely  fixed, 
and  possessing,  with  the  exception  of  one  group,  a  system 
of  foot-like  processes  (ambulacra),  which  may  be  inflated 
with  water  through  ambulacral  vessels,  communicating  by 
means  of  a  peculiar  canal  (madreporic  body)*  with  the  ex- 
terior. The  spaces  between  the  ambulacral  pores  are  the 
ambulacral  spaces. 

The  majority  of  Echinodermata  are  more  or  less  enclosed 

*  So  called  from  the  resemblance  its  sieve-like  opening  bears  to  a  polyp 
chamber  of  Madrepora. 


CLASSIFICATION.  17 

by  a  complicated  system  of  calcareous  plates,  giving  a 
rigidity  to  the  general  form  of  the  animal. 

The  plates  constituting  the  dorsal  system  may  be  very 
numerous  and  complicated,  so  as  to  form  a  stem  by  which 
the  animal  is  invertedly  attached  to  the  ground,  while  the 
ambulacral  system  may  be  limited  to  a  comparatively  small 
area,  and  the  interambulacral  system  is  wanting,  as  in  Coma- 
tula  (sea  lily);  the  dorsal  system, though  large,  may  not  form 
a  stem,  yet  fold  over  on  the  under  side  of  the  animal  so  as  to 
enclose  entirely  the  ambulacral  system,  forming  a  kind  of 
shield  to  the  bases  of  the  long  snake-like  arms,  as  in  Ophio- 
pholis  ;  the  system  may  occupy  the  back  of  the  animal,  but 
not  to  enclose  the  ambulacral  suckers  which  find  their  way 
between  the  rows  of  small  plates  along  the  under  side  of  the 
arms,  as  in  Asteracanthion  (star  fish) ;  the  system  may  be 
contracted  to  a  small  area  on  the  top  of  the  animal,  the  rows 
of  interambulacral  plates  which  are  separated  and  lie  on 
either  side  of  the  ambulacra  in  the  star  fish  may  now  be 
united,  and  both  ambulacral  and  interambulacral  systems 
bent  upward,  meeting  in  a  small  dorsal  area  above,  as  in  Tox- 
opneustes  (sea  urchin) ;  or  the  ambulacral  and  interambulacral 
systems  may  take  a  great  preponderance  over  the  dorsal  sys- 
tem, the  latter  being  pushed  out  to  the  end  of  a  cylinder, 
while  the  two  former  run  along  its  whole  length,  as  in  Holo- 
ihuria  (sea  cucumber). — (E.  C.  &  A.  Agassiz.) 

SAC  (Mollusca). 

A  mollusc  has  the  stomach  and  viscera  enclosed  by  a  fleshy 
sac.  Principal  nerve  masses,  consisting  of  ganglia,  which 
are  adjacent  to,  or  surround  the  oesophagus.  Intestine  bend- 
ing inward,  or  having  an  outward  flexure.  Heart  on  outer 
side  of  intestine.  (Morse.) 

Divided  into  Polyzoa,  Brachiopoda,  Tunicata,  Lamellibran- 
chiata,  Gasteropoda,  Pteropoda,  and  Cephalopoda. 

Polyzoa. — Compound  molluscs.  Respiratory  apparatus 
exsertile  from  sac  in  the  form  of  ciliated  tentacles  around 
mouth.  Intestinal  canal  definite,  curved  upon  itself.  Single 
ganglion  situated  at  re-entering  angle.  Heart,  none. 

Brachiopoda. — Animals  solitary.     Mantle  covered  by  bi- 


18  COMPARATIVE   ANATOMY. 

valved  shell,  arranged  antero-posteriorly  to  body.  Respira- 
tory apparatus  in  the  form  of  two  long,  ciliated  tentacles. 
Alimentary  canal  curved  upon  itself,  and  either  ends  blindly 
in  the  middle  line  or  else  terminates  in  a  distinct  line  be- 
tween lobes  of  mantle.  (Huxley.)  Nervous  ganglion  placed 
within  the  re-entering  angle  of  intestine.  Vascular  system 
imperfectly  understood.  An  atrial  circulation,  or  movement 
of  water  within  system  of  communicating  chambers,  is  well 
developed. 

Tunicata. — Compound  or  single  molluscs.  Respiratory 
apparatus  included  within  mantle.  Gullet  commences  from 
the  base  of  this  branchial  chamber.  Endostyle*  present. 
The  intestine  is  curved  upon  itself  and  terminates  at  anal 
aperture,  which  is  always  situated  within  a  chamber  opening 
externally  by  a  second  aperture  upon  mantle.  The  nervous 
ganglion  not  placed  within  entering  angle  of  intestinal  fold. 
Heart  of  simple  form  always  present.  Atrial  system  present 
as  in  Brachiopoda. 

Lamellibranchiata. — Solitary  molluscs.  Shell  bivalved, 
arranged  to  right  and  left  half  of  mantle.  Respiratory  ap- 
paratus in  the  form  of  lamellae  and  are  four  in  number,  two 
on  either  side  of  visceral  mass.  Mouth  often  furnished  with 
labial  lobes.  The  intestine  generally  penetrates  the  heart, 
and  terminates  near  anus  between  the  mantle  lobes  at  pos- 
terior extremity  of  body.  Nervous  ganglia  generally  of  three 
pair,  arranged  as  follows :  one  for  the  parts  about  the  mouth, 
one  for  the  foot,  when  present,  and  the  remaining  one  for  the 
posterior  adductor  muscle.  The  heart,  often  of  two  cham- 
bers, occasionally  of  one. 

Gasteropoda. — Solitary  molluscs.  Shell  univalved  or  mul- 
tivalved;  whorls  dextral,  as  a  rule.  Respiratory  appara- 
tus; comb-like  gills  in  aquatic,  lung-like  structure  in  terres- 

*  The  middle  of  the  haemal  wall,  viz.,  the  side  toward  the  heart,  the  pharynx, 
is  pushed  into  a  longitudinal  fold,  the  bottom  of  which  projects  into  a  blood 
sinus,  and  has  a  much  thickened  epithelial  lining.  Viewed  from  one  side  the 
bottom  of  the  fold  consequently  appears  like  a  hollow  rod,  and  has  been 
termed  the  "endostyle."  The  functions  of  this  structure  are  unknown. 
(Huxley.) 


CLASSIFICATION.  .  19 

trial  types.  Alimentary  canal  bent  upon  itself,  the  rectum 
very  commonly  opening  into  the  mantle  cavity  above  the 
cephalic  portion  of  body.  (Huxley.)  Nervous  system,  same 
plan  as  Lamellibranchiata — tendency  to  aggregation  of  gan- 
glia toward  cephalic  extremity.  Foot  constantly  present. 

Pteropoda. — Shell  univalve,  if  any.  Alimentary  canal  and 
nervous  ganglia  resembling  in  arrangement  those  of  Gastero- 
poda. Cephalic  extremity  rudimentary. 

Cephalopoda. — Shell  univalved,  either  elaborate,  rudiment- 
ary or  absent.  Respiratory  apparatus  by  gills,  either  in  one 
or  two  pairs.  Alimentary  canal  and  nervous  ganglia  as  the 
last  two  groups.  The  margins  of  foot  are  produced  into 
more  or  less  numerous  tentacular  appendages,  often  pro- 
vided with  singularly  constructed  suckers  or  acetabula, — the 
mouth  being  situated  at  a  central  point. 

EING  (Articulata). 

The  embryo  of  an  articulate  is  evolved  from  the  ventral 
aspect  of  the  ovum,  and  presents  serrated  borders.  In  adult 
condition  articulates  present  a  series  of  rings  joined  together 
by  intervening  tissues.  In  the  lower  groups,  as  Rotifera, 
Entozoa,  and  Annelida,  this  arrangement  is  less  evident  than 
in  the  higher;  hence  these  animals  are  by  some  separated 
from  the  Articulata  and  termed  the  Annulosa.  A  single 
ring  of  an  articulate  animal  thus  characterized  contains  a 
portion  of  the  main  blood-vessel,  nervous  system  and  ali- 
mentary canal,  arranged  in  the  following  order :  blood-vessel 
under  dorsal  surface,  nervous  system  on  the  ventral,  and  the 
alimentary  canal  between.  At  the  cephalic  extremity  of  the 
animal,  this  arrangement  is  modified  by  the  nerves  at  that 
point  forming  a  collar  or  ring  (cesophageal  ring)  around  the 
gullet,  which  then  terminates  toward  dorsal  aspect  of  seg- 
ments. The  organs,  as  a  rule,  are  arranged  upon  either  side 
of  a  longitudinal  axis.  Divided  into  Rotifera,  Entozoa,  An- 
nelida, Crustacea,  Myriapoda,  Arachnida,  and  Insecta. 

Rotifera.  —  Aquatic,  limbless  articulates.  Cephalic  ex- 
tremity furnished  with  a  retractile  (often  lobed)  disk,  upon 
which  are  usually  placed  cilia.  Water  vascular  system 
present. 


20  COMPARATIVE   ANATOMY. 

Entozoa. — Definition  obscure.  "Water  vascular  system 
present.  As  name  expresses,  its  forms  are  parasitic. 

Annelida. — Worm-like  articulates.  Division  into  rings 
occasionally  obscure  or  rarely  absent.  Limbs  without  articu- 
lations. Alimentary  canal  floating,  with  anus  dorsal.  Cilia 
present.  Blood-vessel  system  complete. 

Crustacea. — Aquatic  articulates.  Segments  of  head  and 
thorax  combined  (cephalothorax) ;  intestine  straight;  all  pass 
through  a  series  of  metamorphoses  in  development— all  un- 
dergo exuviation  ;  all  respire  by  branchiae  or  by  surface  of 
body  performing  function  of  aeration.  (Dana.) 

Myriapoda. — Air-breathing  articulates.  Legs  numerous — 
fewer  in  young  than  adult. 

Arachnida. — Air-breathing  articulates.  Segments  of  head 
and  thorax  combined  (cephalothorax) ;  legs,  eight  at  maturity. 

Insecta. — Air-breathing  articulates.  Head  distinct  from 
thorax ;  legs,  six ;  body  permeated  with  air :  often  winged. 

VERTEBRA  (Yertebrata). 

The  embryo  of  a  vertebrate  is  evolved  from  the  dorsal 
aspect  of  the  ovum ;  a  chorda  dorsalis  (notochord)  is  placed 
beneath  a  dorsal  median  groove ;  an  internal  skeleton  is  al- 
ways present,  composed  of  cartilaginous  or  osseous  segments. 
These  segments  are  thought  to  be  modified  portions  of  a 
number  of  typical  vertebrae,  each  vertebra  being  composed 
of  a  centrum  (body),  neurapophysis  (lamina),  neural  spine 
(spinous  process),  diapophysis  (transverse  process),  zygopo- 
physis  (oblique  process),  pleurapophysis  (rib),  hsemapophysis 
(intercostal  cartilage),  haemal  spine  (segment  of  sternum), 
epipophysis  (spine  above  centrum),  and  hypopophysis  (spine 
below  centrum).  The  cavity  defined  above  the  centrum  is 
the  neural  canal ;  that  below  the  centrum,  the  haemal  canal. 
By  this  method  the  plan  of  the  Yertebrata  might  be  compared 
to  a  double  ring — the  upper  designed  for  the  reception  of  the 
neural  axis;  the  lower  for  the  blood-vessel  and  digestive  sys- 
tems, together  with  the  sympathetic  nerve. 

Motion  of  jaw  up  and  down.  Complete  vascular  and  lym- 
phatic systems  with  portal  circulation,  spleen,  and  valvular 
heart  present,  except  in  Amphioxus  (lancelet).  The  organs 


CLASSIFICATION.  21 

of  a  vertebrate  animal  possess  a  tendency  to  arrange  them- 
selves on  either  side  of  a  longitudinal  axis. 

Pisces. — No  amnion  or  allantois.  Posterior  or  visceral 
clefts  persistent,  bearing  branchise*  (gills)  throughout  life. 
Limbs,  properly  so  called,  absent;  fins  median  and  rayed; 
nasal  sacs,  as  a  rule,  do  not  communicate  with  a  mucous 
surface;  blood  corpuscles  nucleated  and  red,  with  exception 
of  Amphioxus  (lancelet),  which  are  colorless ;  heart  with  one 
auricle  and  one  ventricle,  with  the  exception  of  Amphioxus; 
skull  articulates  with  vertebral  column  through  single  sur- 
face, the  basi-occipital  bone;  lower  maxillary  articulates  with 
skull  through  a  chain  of  bones  (suspensorium),  and  presents 
a  concave  articular  surface. 

Batrachia. — No  amnion  or  allantois.  Posterior  visceral 
clefts  generally  closing  in  adult,  so  that  branchiae  are  pres- 
ent in  the  majority  of  cases  only  in  the  young.  Limbs  pres- 


*  "It  is  at  the  beginning  of  the  intestinal  canal,  where  the  ventral  laminae 
are  converging,  that  the  branchial  arches  are  developed ;  the  parietes  of 
the  body  here  become  thinner ;  and  in  this,  the  cervical  region,  several  clefts 
or  fissures  make  their  appearance,  which  sink  downward,  and  penetrate 
through  the  mucous  layer ;  there  are  three  pairs,  or,  with  the  oval  aperture, 
four  pairs  of  such  fissures,  but  the  posterior  pair  are  extremely  small ;  they 
are  called  the  branchial  fissures — fissures  branchiales ;  between  them  lie 
three  segments,  or  divisions  of  the  ventral  laminae,  which  are  blunt  and 
rounded  anteriorly,  beveled  off  toward  the  digestive  cavity,  and  therefore 
sickle-shaped;  these  are  named  the  branchial  arches — arcus  branchiales; 
the  fourth  branchial  arch  is  placed  hindmost,  and  is  not  yet  distinct  from 
the  ventral  lamina.  On  the  fourth  day  the  two  most  anterior  branchial 
arches  increase  in  thickness;  a  new  fissure  is  formed  posteriorly;  on  the 
fifth  day  the  foremost  fissure  closes,  and  the  foremost  branchial  arch  unites 
with  its  fellow  of  the  opposite  side,  and  forms  the  lower  jaw ;  the  next  in 
succession  is  transformed  into  the  os  hyoides.  The  two  last  branchial  fis- 
sures close  upon  the  fifth  day;  at  the  same  time  the  first  is  lost  entirely; 
but  the  second  continues  longer  open.  On  the  third  and  fourth  days  the 
part  of  the  ventral  lamina,  which  is  situated  in  front  of  the  lower  jaw,  thick- 
ens, and  resolves  itself  into  the  lower  jaw ;  this  part  is  more  strongly  marked 
on  the  fifth  day.  The  two  sides  of  the  upper  jaw  do  not  meet  in  the  first 
instance  ;  they  coalesce  at  a  later  period,  through  the  medium  of  the  frontal 
process  which  is  developed  betwixt  the  eye."  —  Extract  from  chapter  on 
in  Wright's  trans,  of  Wagner. 


22  COMPARATIVE   ANATOMY. 

ent;  blood  corpuscles,  red  and  always  nucleated;  nasal  sacs 
communicate  with  a  mucous  surface  (mouth);  heart  with 
two  auricles  and  a  single  ventricle;  skull  articulates  by  dou- 
ble surfaces  through  ex-occipital  bones;  basi-occipital  carti- 
laginous; suspensorium  less  complex  than  in  Pisces;  lower 
maxillary  presents  a  concave  articular  surface. 

Reptilia. — Amnion  and  allantois  present.  Posterior  vis- 
ceral arches  always  closed,  consequently  no  branchiae;  skull 
articulates  through  single  surface,  composed  of  a  basi-occi- 
pital and  two  ex-occipital  elements;  suspensorium  consists 
of  a  single  bone  (os  quadratum);  lower  maxillary  presents  a 
concave  articular  surface. 

Aves. — Same  as  Reptilia,  with  the  additional  characters — 
union  of  first  row  of  tarsal  bones  with  lower  end  of  tibia,  and 
second  row  with  metatarsus;  metatarsal  elements  anchy- 
losed,  excepting  in  Aptenodytes  (penguin);  aorta  turns  to 
right;  bronchial  tubes  open  into  air  sacs  communicating 
generally  with  the  interior  of  the  bones;  skin  furnished  with 
feathers. 

Mammalia. — Amnion  and  allantois  present.  Posterior 
visceral  arches  always  closed;  red  blood  corpuscles  non- 
nucleated  ;  diaphragm  complete ;  skull  articulates  by  double 
surfaces,  each  of  which  is  composed  of  elements  from  the 
basi-occipital  and  ex-occipital  bones ;  cervical  vertebrae  seven 
— apparent  exception  in  Bradypus  (sloth);  lower  jaw  articu- 
lates directly  with  skull  by  a  convex  condyle;  mammary 
gland  present;  skin  furnished  with  hair. 

Each  of  the  above  plans  is  distinct.  No  member  of  one 
plan  possesses  a  tendency  to  run  into  another.  A  few  dis- 
puted forms  have  held  doubtful  positions,  such  as 

Sipunculus.  —  Really  articulate  (through  JEchiurus)  in  ar- 
rangement of  viscera  with  respect  to  a  longitudinal  axis,  dis- 
position of  blood-vessel  and  muscular  systems,  and  in  dorsal 
position  of  anus.  Apparently  radiate  (through  Holothuria) 
in  general  appearance,  habit,  arrangement  of  oral  tentacles, 
.tortuous  alimentary  canal  enclosed  by  folds  of  peritoneum, 
and  structure  of  integument. 

Dentalium. — Really  molluscoid  in  presence  of  mantle,  heart, 


THE   SKELETON.  23 

protrusile  foot,  and  in  curvature  of  alimentary  canal.  Appa- 
rently annelidous  in  shape  of  shell,  and  red  color  of  blood,  as 
well  as  annulated  form  of  embryo. 

The  following  forms  have,  until  recently,  held  doubtful 
positions  among  classes  of  Vertebrata : 

Lepidosiren. — Really  piscine  in  arrangement  of  gill  arches, 
in  construction  of  scapular  arch,  and  fin  rays,  and  in  single 
auricle  to  heart.  Apparently  reptilian  in  external  gill  and 
position  of  nares. 

Labyrinthodon. — Really  batrachian  in  presence  of  double 
occipital  condyle,  parasphenoid  and  'girdle'  bones.  Appa- 
rently saurian  in  length  of  ribs,  and  development  of  dermal 
plates. 

Archceopleryx. — Really  avine  in  union  of  tarsal  and  rneta- 
tarsal  elements,  and  presence  of  feathers.  Apparently  saurian 
in  prolonged  production  of  vertebrae  in  a  caudal  series,  pres- 
ence of  teeth,  and  construction  of  pelvis. 

Ornithorhynchus. — Really  mammalian  in  presence  of  mam- 
mary gland,  direct  articulation  of  lower  jaw  to  skull,  complete 
diaphragm,  and  the  fixity  of  inferior  strait  of  pelvis.  Ap- 
parently avine  in  presence  of  webbed  foot,  spur,  and  duck- 
like  bill. 


III. 

SKELETON, 

THE  SKELETON  is  the  framework  of  the  body.  It  protects 
the  internal  organs,  while  affording  points  of  attachment  to 
ligaments  and  muscles.  It  may  be  diffuse  or  compact. 

The  diffuse  is  composed  of  sclerous  particles  scattered 
throughout  the  tissues,  having  no  fixed  union  with  one  an- 
other, and  little  or  no  power  to  retain  the  general  form  of 
animal  after  the  removal  of  the  soft  parts.  The  compact  is 
either  composed  of  a  solid  mass  encompassing  the  organism 
in  a  single  piece,  as  in  Helix  (snail),  or,  being  made  up  of  ar- 


24  COMPARATIVE   ANATOMY. 

ticulated  segments,  is  placed  externally  to  the  soft  parts,  as  in 
Articulata,  or  arranged  to  them  as  a  central  longitudinal  axis, 
as  in  Vertebrata. — The  compact  variety  generally  conforms 
to  the  type  to  which  the  animal  belongs.  Thus,  in  Radiata 
it  is  rayed,  in  Mollusca  the  mantle  is  calcified  in  one  or  more 
plates,  and  in  the  Articulata  and  Vertebrata  the  parts  and 
accessories  of  the  ring  and  vertebra  are  respectively  main- 
tained. 

The  skeleton  may  arise  from  animals  whose  tissues  are 
not  otherwise  specialized,  while  in  those  highly  organized  it 
is  often  absent.  Thus,  Nanomia,  a  foraminiferous  rhizopod, 
possesses  an  elaborate  skeleton,  while  with  Doris,  a  gas- 
teropod  mollusc,  a  few  calcareous  spicules  are  alone  present. 
"Within  a  natural  group  it  may  be  absent  (Amoeba),  diffuse 
( Thallasicolla,  Sphcerozoum),  or  compact  (Foraminifera). 

The  skeletons  of  composite  animals,  as  Polypi  and  Polyzoa, 
resemble  one  another  more  or  less  intimately. 

The  presence  of  the  skeleton  is  determined  by  habit. 
Lowly  organized  animals,  if  floating  (Aurelia,  Physalia),  often 
have  no  skeletons;  but  if  fixed  (coralline  polyps)  or  moving 
upon  a  ground  surface  (Echinodermata),  they  are  generally 
present. 

Skeletons  are  of  various  composition,  viz. :  calcareous,  cor- 
neous, chitinous,  siliceous,  cartilaginous,  or  osseous.* 

PROTOZOA.  In  Foraminifera  the  sareodous  mass  is  con- 
tained within  a  chambered  shell,  having  perforate  walls  and 
partitions,  successive  cells  being  added  by  a  process  of  gem- 
mation. The  form  of  the  shell  is  subject  to  great  variety, 
the  prevalent  shapes  being  modifications  of  the  disk  or  spiral. f 
In  Eozoon,  an  extinct  genus  of  Protozoa,  allied  to  the  Fora- 
minifera, the  skeleton  is  deposited  between  layers  of  sarcode 

*  A  '  false  skeleton '  is  an  agglutination  of  extraneous  matter  fixed  to 
the  animal  by  cutaneous  secretion,  as  in  Terebella. 

f  So  minute  are  these  shells  that  it  is  estimated  that  6000  can  be  counted 
in  a  grain,  and  3,800,000  in  an  ounce  of  foraminiferous  sand.  The  pyramids 
of  Egypt  are  built  of  what  is  known  as  nummulitic  limestone,  so  called  from 
the  bulk  of  the  stone  being  chiefly  due  to  the  presence  of  enormous  num- 
bers of  a  species  of  Foraminifera  (Nummulus). 


THE    SKELETON.  25 

(q.  v.)  as  perforate  masses  of  calcareous  matter  of  no  determ- 
inate figure.  The  remains  of  such  skeletons  form  immense 
deposits  in  the  earth's  crust.  In  Thallasicolla  (sea  jelly),  the 
large  cells  composing  the  mass  are  loosely  connected  by  sili- 
ceous spicules.  In  Lithocampa,  the  skeleton  is  compact,  dome- 
shaped,  with  the  cyst  contained  within  the  dome.  The 
sarcodous  mass  is  protruded  at  will  through  numerous  fenes- 
trae.  In  Infusoria,  the  skeleton  is  membranous,  ciliated,  has 
the  precise  form  of  the  animal,  and  is  often  furnished  with 
spine.  In  Ceratium,  two  horn-like  processes  are  appended  to 
a  reticulated  shell. 

RADIATA.  Ccelenterata.  Polyps  naked.  In  Alcyoniumy 
integument  with  granules  of  lime  interspersed  without  order 
or  forming  calcareous  masses — coral.  These  last  are  (1)  fixed, 
rigid,  as  in  Madrepora,  or  segmented,  with  corneous  tissue, 
with  or  without  spicules  intervening,  as  in  Isis  and  Gorgorda; 
(2)  root  loosely  inserted  in  the  bottom  of  the  sea,  of  a  leathery  consist- 
ence, as  in  Pennatula  (sea  pen),  or  having,  in  addition,  granules 
of  lime  interspersed,  as  in  Renilla. — In  Acalephoe,  the  hydroid 
stock  of  Hydroida  is  either  coriaceous,  branched,  furnished 
with  hydra  cups  and  capsules,  or  naked.  In  Millepora  alone 
is  there  a  calcareous,  coral-like  skeleton.  Porpita  has  a  circu- 
lar, radiate,  calcareous  disk;  Velella,  an  upright  triangular 
crest.  The  Discophorse  are  naked. 

Echinodermata. — Segmented  in  all ;  mobile,  as  in  Pentacri- 
nus,  Comatula,  Asterophyton,  Asteracanthion  ;  fixed  as  in  Toxo- 
pneustes  (sea  urchin)  and  Spatangus;  diffuse,  as  in  Holothuria 
and  Psolus  squamatus ;  calcareous  cesophageal  ring  present  in 
latter  group.  In  Synapta,  curious  anchor- shaped  appendages 
to  skin.  Deciduous  form  of  skeleton  seen  in  larval  form  of 
Toxopneustes.  (See  p.  127.) 

MOLLUSCA.  Polyzoa. — Skeleton  compact  for  accommoda- 
tion of  many  individuals ;  each  cell  perforate  from  within  to 
accommodate  protrusions  of  visceral  sac. 

Brachiopoda. — Skeleton  bivalved  (shell),  placed  to  the  body 
antero-posteriorly ;  opened  by  spiral  valve. 

Tunicata  rarely  with  skeleton.  Spicules  of  carbonate  of 
lime,  resembling  raphides  of  plants,  not  unfrequent  in  mantle; 


26 


COMPARATIVE   ANATOMY. 


In  Chelyosoma,  shell  tesselated;  Chevreulius,  bivalved.  Bol~ 
tenia  has  calcareous  granules  at  pedicle.  Siliceous  particles 
in  integument  of  Salpa. 

Lamellibranchiata. — Skeleton  bivalved  (shell),  placed  right 
and  left  to  body ;  opened  by  elastic  ligament  at  hinge.  The 
line  of  hinge  may  be  toothed  or  smooth. 

Gasteropoda. — Skeleton  generally  univalved  (shell).  Oper- 
culum,  a  horny  or  calcareous  disk  attached  to  foot  and  em- 
ployed in  opening  and  closing  mouth  of  shell.  It  is  supposed 
by  some  to  represent  the  second  valve  of  the  Lamelli- 
branchiata. Shell  generally  whorled  from  right  to  left, 
rarely  from  left  to  right  as  in  Physa\  rudimentary  in  Limax 
(slug),  multivalvular  in  Chiton. 

Pteropoda.  —  Skeleton  (shell)  univalved;  papery,  as  in 
Hyalea  arid  Cleodora. 

Cephalopoda. — Skeleton  of  two  kinds,  external  and  in- 
ternal. External,  representing  the  shell  of  other  molluscs, 
is  univalved,  and  may  be  either  an  elaborate  chambered 
shell  (Nautilus),  or  rudimentary.  When  of  the  latter  kind,  it 
is  developed  from  the  dorsum  of  mantle,  and  is  made  up 
within  a  closed  sac  of  a  number  of  corneous  pen-like  bodies, 
as  in  Loligo  (squid),  or  a  single,  light,  calcareous  piece,  as  in 
Sepia  (cuttle-fish).  Such  skeletons  are  used  as  floats. — Internal 
form  is  cartilaginous.  It  is  confined  to  four  segments  sur- 
rounding the  brain,  named  as  follows :  brachial,  cephalic, 
dorsal,  and  articular.  This  is  the  first  appearance  of  an  in- 
ternal skeleton  in  the  animal  kingdom. 

Structure  of  skeleton  of  molluscs  is  chiefly  that  of  columns 
of  calcareous  matter  arranged  transversely  to  the  shell. 
Great  variety  exhibited  in  the  detail  of  arrangement  of  these 
columns.  Inner  layer  porcellaneous;  outer  layer  epidermic; 
nacreous  layer  (mother-of-pearl),  when  present,  in  the  inner 
aspect  of  porcellaneous  layer.  Pearls  are  formed  by  a  depo- 
sition of  the  secretion  of  the  nacreous  layer  upon  some  ex- 
traneous body  lying  between  the  mantle  and  the  shell.  This 
may  be  a  grain  of  sand  or  the  body  of  a  parasite. 

Tubular  structure  of  nacreous  table  in  Anomia  and  Area; 
to  the  perforate  type  in  Brachiopoda,  few  exceptions  known. 


THE   SKELETON.  27 

Shells  mostly  composed  of  carbonate  of  lime.  Lingula  an 
exception  (phosphate  of  lime). 

Shells  grow  in  thickness  and  in  length;  the  former  is  se- 
cured by  secretion  from  the  mantle  everywhere  excepting  at 
the  edge.  Here  growth  in  length  takes  place,  as  the  shell 
extends.  The  shell  may  be  variously  colored  by  the  secre- 
tion of  pigment  cells.  Growth  is  periodic.  Lines  of  growth, 
therefore,  furnish  an  index  to  age.  The  muscles  employed 
in  closing  valves  of  certain  molluscs  move  their  bases  at  each 
time  of  growth,  so  that  the  same  relative  position  of  the  parts 
of  the  shell  may  be  maintained. — Byssus  is  the  hardened, 
cord-like  secretion  of  a  peculiar  gland  seen  in  certain  bivalve 
molluscs.  Fastened  by  one  extremity  to  some  submerged 
object,  the  other  being  in  relation  to  the  shell,  the  individual 
obtains  through  the  byssus  a  secure  anchorage. 

ARTICULATA.  Skeleton  external,  composed  of  a  number 
of  rings  joined  by  fibrous  structures.  May  be  chitinous  or 
calcareous ;  diffuse  or  compact. 

Annulations  obscure  in  many  Entozoa  and  Annelida. 

Anus  terminal  in  Crustacea,  Myriapoda,  Arachnida,  In- 
eecta:  dorsal  and  generally  terminal  in  Annelida;  not  con- 
stantly terminal  in  Rotifera  or  Entozoa. — Rudimentary  forms 
of  skeleton  in  Entozoa.  Extraneous  skeletons  in  Tubicola 
and  in  larva  of  Phrygana. 

Structure  epidermoid,  as  in  Lytta ;  tubular  in  Scolopendra 
(centipede),  Limulus  (king-crab),  and  Balanus  (acorn  barnacle). 

Certain  articulates,  as  Crustacea  and  some  larval  forms  of 
Insecta  (Cicada),  shed  their  skeletons  periodically.  This  is 
called  exigesis. 

Limbs  and  wings  are  appendages  to  the  segments.  Limbs 
may  be  without  joints  (setae),  as  in  Annelida,  or  jointed  (ar- 
thropod), as  in  Insecta.  Wings  are  confined  to  Insecta. 

VERTEBRATA.  The  vertebrate  skeleton  is  a  central  seg- 
mented, longitudinal  axis.  Of  two  kinds,  cartilaginous  and 
osseous.  In  the  cartilaginous  form,  confined  to  certain  fishes, 
the  chorda  dorsalis  is  persistent.  In  the  osseous  form  assem- 
blages of  bones  are  seen,  developed  for  the  most  part  from  a 
cartilaginous  basis.  Those  arising  from  another  source  are 


28  COMPARATIVE   ANATOMY. 

called  membrane  bones;  and  may  form  either  in  the  peri- 
chondrium,  or,  as  in  the  case  of  certain  cranial  bones,  in 
the  membranous  roof  continuous  with  the  perichondrium. 
(Huxley.) — In  conjunction  with  the  osseous  skeleton  are 
often  found  portions  of  a  cartilaginous  framework  more  or 
less  complete.  This,  for  the  most  part,  is  confined  to  the 
cranium,  and  is  best  expressed  in  the  heads  of  Batrachia  and 
certain  fishes,  as  in  Eana  (frog),  and  JEsox  (pike).  With  the 
higher  Vertebrates  it  becomes  less  defined,  until  in  man  it  is 
thought  to  be  represented  in  the  small  cartilage  occupying 
the  median  lacerated  foramen  at  base  of  skull.  This  carti- 
lage, together  with  a  few  others,  such  as  the  tracheal  and 
auricular  cartilages,  never  ossifies. 

The  study  of  the  osseous  vertebrate  skeleton,  with  a  view 
of  instituting  comparisons  between  it  and  that  of  man,  should 
at  all  times  be  pursued  in  conjunction  with  the  study  of  its 
development.  In  no  other  way  can  the  construction  of  the 
skeleton  be  understood.  As  an  approximation  to  truth  it 
may  be  stated,  that  every  centre  of  ossification  stands  for  a 
bone,  and  therefore  that  there  are  as  many  bones  in  a  skel- 
eton as  centres  of  ossification.  The  actual  number  in  the 
adult  skeleton  of  the  majority  of  animals,  however,  is  much 
smaller  than  its  centres  of  development :  a  result  obtained 
from  the  tendency  of  centres  to  group  themselves  into  cer- 
tain forms  which  are  fixed  and  definite  within  recognized 
limits.  Thus  while  any  portion  of  a  skeleton,  resulting  from 
the  union  of  two  or  more  centres,  is  for  convenience  called  a 
bone,  it  is  in  reality  an  assemblage  of  bones.  In  the  osseous 
fish  there  is  no  occipital  bone;  but  its  place  is  taken  by  a 
number  of  bones  called  basi-occipital,  ex-occipital,  and  supra- 
occipital.  Now  in  man  the  occipital  bone  is  proved  by  de- 
velopment to  be  the  union  of  the  three  portions  seen  in  the 
skeleton  of  the  fish,  and  is,  therefore,  not  a  bone,  but  an 
association  of  bones. 

In  like  manner  the  sphenoid  bone  of  man  is  divisible  into 
basi-sphenoid,  pre-sphenoid,  ali-sphenoid,  orbito-sphenoid, 
and  internal  pterygoid.  The  frontal,  into  right  and  left 
frontal;  to  which  are  added,  anterior  and  posterior  frontal 


THE   SKELETON.  29 

elements.  The  temporal,  into  squamosal,  tympanic,  mastoid, 
epiotic,  opisthotic,  and  pro-otic.  The  superior  maxillary, 
into  maxillary  proper  and  intermaxillary.  The  lower  max- 
illary, into  angular,  articular,  opercular,  and  dentary  bones. 

As  a  rule,  the  tendency  to  union  increases  as  we  ascend 
the  vertebrate  scale.  Exception  in  Batrachia,  where  the 
frontal  and  parietal  bones  of  either  side  are  united. 

Pisces. — Skull  articulates  with  vertebral  column  through 
body  of  occipital  bone  and  first  cervical  vertebra.  Bones  of 
face  greatly  developed.  First  and  second  cervical  vertebrae 
very  large.  Vomer  of  great  size,  often  tooth-bearing;  supe- 
rior maxillaries  of  small  size,  rarely  tooth-bearing;  inter- 
maxillary bones  always  distinct;  para-sphenoid  bone  ex- 
tending antero-posteriorly  beneath  cranial  series.  Inferior 
maxillary  bone  represented  in  five  centres  on  either  side, 
recognized  as  dentary,  articular,  angular,  and  opercular 
bones;  the  fifth  is  obscure.  The  articulation  between  bodies 
of  vertebrse  markedly  biconcave.  Bones  generally  flat,  never 
hollow;  sutures  generally  squamosal,  rarely  serrate. 

Batrachia.  —  Skull  articulates  with  vertebral  column  by 
two  condyles  on  ex-occipital  bones.  Basi-occipital  cartila- 
ginous. 'Girdle  bone/  placed  in  anterior  part  of  cranial 
cavity  of  frog-like  Batrachia,  represents  the  ethmoidal  and 
orbito-sphenoidal  elements  of  skulls  of  higher  vertebrates. 
Para-sphenoid  present  as  in  Pisces.  Frontal  and  parietal 
elements  on  either  side  united  into  a  single  bone — the  fronto- 
parietal.  Bodies  of  vertebrae  may  articulate  by  double  con- 
cave surfaces,  as  in  Spderpes  (salamander),  by  convex  surface 
in  front  and  concave  behind,  as  in  Hana  (frog).  Long  bones 
very  generally  without  epiphyses;  exception  in  femur  of 
Hana;  tibia  and  fibula  of  same  animal  united  in  one  shaft. 
Lower  jaw  commonly  composed  of  three  bones— dentary, 
angular,  and  articular. 

Reptilia. — Skull  articulates  with  vertebral  column  by  a 
single  condyle  formed  by  portions  of  basi-occipital  and 
ex-occipital  bones.  Para-sphenoid  absent.  Basi-sphenoid  re- 
markably compressed  antero-posteriorly  in  Crocodilia.  The  pe- 
culiar '  transverse '  bone  extends  from  the  internal  pterygoid 


30  COMPARATIVE   ANATOMY. 

to  the  point  of  junction  between  the  zygomatic,  the  maxil- 
lary, and  the  post-frontal  bones.  Chevron  bones  are  lateral 
appendages  to  cervical  vertebrae,  and  represent  the  transverse 
processes  of  the  corresponding  bones  in  Mammalia. — Bodies 
of  vertebra  articulate  by  double  concave,  or  ball-and-socket 
joint.  Bones  without  epiphyses,  generally  solid;  hollow  in 
Dinosauria.  Carapax  and  plastron  portions  of  skeleton  of 
Chelonia  are  modified  vertebral  segments.  Inferior  maxil- 
lary bone  possesses  five  distinct  centres — dental,  angular, 
opercular,  articular,  and  two  smaller  pieces  seen  upon  the 
inner  surface.  Bones  of  skull  commonly  united  by  perma- 
nent suture,  excepting  in  Ophidia  and  majority  of  Chelonia, 
where  they  are  early  consolidated. 

Aves. — Articulation  of  skull  as  in  Reptilia.  Articulations 
of  cervical  vertebrae  allowing  free  motion;  but  those  of  dor- 
sal and  lumbar  vertebrae  are  immovable.  Ribs  also  fixed; 
conspicuous  posterior  processes.  Sternum  of  a  variety  of 
shapes,  generally  conspicuously  keeled  for  origin  of  great 
muscles  of  flight  (pectorales).  Size  of  coccyx  determined  by 
that  of  tail  feathers;  long  reptilian  extension  in  Archceopteryx 
— bones  generally  hollow;  air  is  admitted,  during  respira- 
tion, into  all  skeletons  as  a  rule,  excepting  terminal  portions 
of  extremities.  In  Hirundo  (swallow),  and  Trochilus  (hum- 
ming-bird), the  bones  are  solid.  Bones  of  skull  unite  by 
early  obliteration  of  sutures,  excepting  Sfruthio  (ostrich). 

Mammalia. — Articulation  with  spine,  by  two  condyles 
made  up  on  either  side  by  union  between  single  basi-occipital 
and  the  two  ex-occipital  bones.  Intermaxillary  bones  unite 
with  superior  maxillary  in  man,  but  remain  separate  in  lower 
mammals.  Spheno-parietal  suture  tolerably  constant  in  car- 
nivorous, as  temporo-frontal  suture  is  in  other  types;  num- 
ber of  cervical  vertebrae  seven, — apparent  exception  in  Brady- 
pus  (sloth) ;  anterior  tubercles  of  the  transverse  process  of  cervi- 
cal vertebrae,  and  the  transverse  processes  of  the  lumbar  verte- 
brae, rudimentary  ribs  (pleurapophyses).  Exo-skeleton  (?)  in 
Edentata.  Inferior  maxillary  bone  probably  composed  of 
the  number  of  centres  seen  in  lower  animals.  Often  com- 
posed of  two  halves  connected  by  cartilage  at  symphysis 


THE    SKELETON.  31 

throughout  life;  or  are  permanently  remote  as  in  Macropus 
(kangaroo). 

Methods  of  articulation  of  inferior  maxillary  to  skull 
vary  in  Vertebrata.  In  Pisces,  it  is  effected  by  means  of  a 
'suspensorium,'  which  is  composed  of  hyomandibular,  sym- 
plectic,pretympanic,  and  hypotympanic  (quadrate)  bones,  with 
opercular  appendages  (gill  covers),  in  turn  composed  of  oper- 
culum,  pre-operculum,  sub-operculum,  and  inter- operculum. 
Suspensorium  of  Batrachia,  Reptilia,  and  Aves,  hypotym- 
panic bone  only,  the  others  having  disappeared.  In  Batrachia 
a  peculiar  hammer-shaped  membrane  bone.,  situated  on  side 
of  face,  may  represent  the  pre-operculum  of  fishes.  (Huxley.) 
No  suspensorium  in  Mammalia;  the  articular  head  of  lower 
jaw  convex  in  this  class, — in  all  others  concave. 

NATURE   OF   LIMBS   IN  VERTEBRATA. 

A  vertebrate  limb  may  be  defined  as  an  articulated  append- 
age, placed  internally  to  soft  parts. 

Pisces. — In  osseous  fishes,  anterior  extremity  united  to 
skull.  Exception,  Anguilla  (eel).  Elements  of  anterior  ex- 
tremity, supra-scapular,  scapular,  and  coracoid  bones;  hu- 
merus,  radius,  and  ulna.  Distal  extremity  without  phalanges, 
but  furnished  with  rays  of  exo-skeleton,  thus  presenting  a 
fin-like  in  place  of  a  hand-  or  foot-like  structure.  Clavicle 
and  posterior  extremity  absent. 

Batrachia  and  Reptilia. — No  supra-scapular  bones;  cora- 
coid bones  large,  often  meeting  at  median  line ;  phalanges 
present.  Posterior  extremity,  with  ilium,  ischium,  and  pubis 
as  separate  bones.  Some  extinct  Reptilia,  tarsal  and  metatar- 
sal  elements  combine.  Phalanges  present.  £ 

Aves. — Anterior  extremity,  with  coracoid  bone  large,  dis- 
tinct from  scapula;  clavicle  (pull  bone,  furcula)  not  joining 
sternum,  but  anchylosed  with  fellow  of  opposite  side ;  pha- 
langes anchylosed  to  form  an  acuminate  apex.  Posterior  ex- 
tremity, with  ilium,  ischium,  pubis,  and  sacrum  anchylosed ; 
tarsus  and  metatarsus  united  to  form  an  elongate  shaft,  ex- 
cepting Aptenodytes  (penguin). 


32  COMPARATIVE   ANATOMY. 

Mammalia. — Scapula  and  coracoid  bones  united,  excepting 
Monotremata ;  clavicle  absent  in  ungulate  quadrupeds,  as  in 
Bos  (bull),  present  in  unguiculates,  as  in  Sdurus  (squirrel). 
In  ungulates  the  ulna  and  fibula  are  often  rudimentary  and 
anchylosed  to  sjiaft  of  radius  or  tibia.  Toes,  never  more 
than  five  to  each  extremity,  enormously  developed  in  length 
in  anterior  extremity  of  Cheiroptera  (bat) ;  joined  with  tar- 
sus and  metatarsus  in  presenting  an  opposing  surface  for 
progression,  in  which  case  all  five  toes  are  present  (planti- 
grade unguiculate),  as  in  Ursus  (bear) ;  tarsus  and  metatar- 
sus elevated,  and  an  opposing  surface  obtained  on  tips  of 
phalanges,  in  which  case  a  number  less  than  five  is  present, 
the  first  toe  commonly  rudimental  or  absent  (digitigrade  un- 
guiculate), as  in  Canis  (dog).  Ungulates  are  properly  digiti- 
grade, and,  excepting  Mephas  (elephant),  have  less  than  five 
toes,  as  follows,  no  mention  being  made  of  the  absent  digits : 
Sus  (hog)  has  third  and  fourth  toes,  with  hoofed  rudiments  of 
second  and  fifth;  Rhinoceros,  second,  third,  and  fifth;  Bos 
(bull),  third  and  fourth,  with  concealed  rudiments  of  second 
and  fifth  metatarsal;  and  Equus  (horse),  third,  with  con- 
cealed rudiments  of  second  and  fourth  metatarsal  (splint 
bones).*  The  elephant  is  thus  seen  to  have  five  toes  to  each 
foot,  the  rhinoceros  three,  the  hog  and  bull  two,  and  the 
horse  but  one. 

In  this  descent  from  five  to  a  smaller  number,  the  toes, 
whether  of  a  plantigrade  or  digitigrade  foot,  are  always  re- 
moved from  the  sides,  and  are  followed  by  loss  of  corre- 
sponding metatarsal  and  tarsal  elements.  But  whatever  their 
number  and  degree  of  development,  the  relations  presented 
between  the  parts  of  a  foot  are  constant;  so  that  in  the  event 
of  absence  of  all  the  toes  excepting  the  third,  the  relations 
of  this  single  toe  to  the  bones  above  it  are  the  same  as  though 
all  five  toes  were  present,  f 


*  The  phalanges  of  the  foot  of  the  horse  are  called,  from  above  down- 
ward, the  pastern,  coronary,  and  coffin  bones. 

f  A  vertebrate  foot  may  be  defined  to  be  that  assemblage  of  bones  placed 
toward  the  distal  portion  of  the  posterior  extremity  beyond  the  tibia.  In 


THE   SKELETON. 


33 


In  examining  the  structure  of  the  foot  of  man  (Fig.  1),  it 
is  observed  upon  the  inner  portion  (I.)  that  the  bones  of  the 
first,  second,  and  third  toes  (1,  2,  3)  articulate  with  their 
metatarsal  elements  (m1,  m2,  m3)  and  each  of  these  with  their 


PLAN  or  CONSTRUCTION  OF  FOOT  OF  MAN. 
— I.  p1,  p2,  p3,  of  each  series  marked  1,  2, 
3,  phalanges,  m1,  first  metatarsal ;  m2, 
second  metatarsal ;  m3,  third  metatarsal 
bone.  cnl,  first  cuneiform ;  en2,  second 
cuneiform ;  cns,  third  cuneiform  bone,  s, 
scaphoid  bone,  a,  astragalus. — II.  p1,  p2,  p3 
of  each  series  marked  4,  5,  phalanges,  m*, 
fourth  metatarsal ;  m5,  fifth  metatarsal  bone, 
cb,  cuboid  bone,  cl,  calcaneum. 


FIG.  2. 


PLAN  OF  CONSTRUCTION  OF 
FOOT  OF  HORSE. — I.  p1,  p»,  ps, 
phalanges  of  series  marked  3. 
m2,  second  metatarsal ;  m3,  third 
metatarsal.  en2,  second  cunei- 
form ;  en8,  third  cuneiform  bone, 
s.  scaphoidbone.  a,  astragalus. — 
II.  m4^  fourth  metatarsal  bone, 
cb,  cuboid,  cl,  calcaueum. 


The  line  *  in  each  cut  indicates  an  axis  of  bones  constantly  present  in  the 
foot  of  every  mammal. 


speaking  of  a  foot  of  a  mammal,  therefore,  reference  is  made  to  the  posterior 
extremity  only.  The  plan  of  construction  of  the  hand — the  analogous  group 
of  bones  in  the  anterior  extremity — is,  however,  essentially  the  same. 

3 


34 


COMPARATIVE   ANATOMY. 


corresponding  cuneiform  (en1,  en2,  en3).  The  three  cunei- 
forms now  articulate  with  the  single  scaphoid  (s),  and  it  in 
turn  with  the  astragalus  (a).  Upon  the  outer  division  (II.) 
the  elements  of  the  fourth  and  fifth  toes  unite  with  the  cuboid 
(cb),  and  it  with  the  calcaneum  (cl). — On  comparing  this  ar- 
rangement with  that  seen  in  the  foot  of  the  horse  (Fig.  2),  the 
inner  portion  of  the  foot  (I.)  is  seen  to  lack  the  elements  of 
the  first  toe  and  metatarsal  bone.  The  second  metatarsal 
series  (2)  is  reduced  to  a  rudiment  of  the  metatarsal  bone 
— inner  splint  bone — (m2),  which  joins  the  second  cuneiform 
(en2).  The  third  series  of  elements  is  perfected,  the  three 
phalanges  (p1,  p2,  p3)  articulate  with  the  third  metatarsal 
(m3),  which  unites  with  the  large  flattened  cuneiform  (en3), 
receiving  the  scaphoid  (s),  which  in  turn  combines  with  the 
astragalus  (a).  The  elements  of  the  outer  part  of  the  foot 
(II.)  are  restricted  to  those  of  the  rudiment  of  the  fourth 
metatarsal  (m4) — outer  splint  bone, — its  phalangeal  series,  as 
well  as  the  segment  of  the  entire  fifth  toe  and  metatarsal 
bone,  being  absent.  The  fourth  metatarsal  (m4)  joins  the 
cuboid,  it  to  articulate  with  the  calcaneum  (cl). 

Table  of  Elements  of  Cranial  Vertebras  of  Man.  (OWEN.) 


OCCIPITAL  VERTEBRA. 

PARIETAL  VERTEBRA. 

Neural  spine.         Supra-occipital. 
Neurapophysis.      Ex-occipital. 
Centrum.                Basi-occipital. 

Pleurapophysis.      Scapula. 
Haemapophysis.     Coracoid  process  of  scapula 
(coracoid  bone). 
Haemal  spine.        1st  joint  of  sternum. 

Parietal. 
Great  wing  of  sphenoid  (alisphenoid). 
Posterior  half  of  body  of  sphenoid  (basi-sphe- 
noid). 
Stylo-hyoid  proc.  and  lig.  (stylo-hyal). 
Lesser  horn  of  hyoid  (cerato-hyal). 

Body  of  hyoid  (basi-hyal). 

FRONTAL  VERTEBRA. 

NASAL  VERTEBRA. 

Neural  spine.          Frontal. 
Neurapophysis.      Lesser   wing   of    sphenoid 
(orbito  frontal). 
Centrum.                Anterior    half  of  body  of 
sphenoid  (pre-sphenoid). 
Pleurapophysis.     Tympanic  portion  of  tem- 
poral (tympanic). 
Heemapophysis.     Ramus  and  angle  of  lower 
jaw  (articular  and  angu- 
lar). 
Haemal  spine.         Mental    portion    of    lower 
jaw  (dentary). 

Nasal. 
Ethmoid. 

Vomer. 
Palatine. 
Superior  maxillary. 

Intermaxillary. 

ARTICULATION.  35 

IV. 

ARTICULATION, 

AN  articulation  is  a  union  of  any  two  sclerous  segments 
of  an  organism  through  the  intervention  of  a  substance  dif- 
fering from  both. 

Synarthrosis  (stiff  joints). 

Sutura — example,  between  bones  of  vertebrate  skull,  and 
exo-skeleton  of  Dasypus  (Armadillo). 

Gomphosis — example,  insertion  of  alveolar  teeth. 

Schindylesis — example,  rostrum  of  sphenoid  with  vomer. 

Amphiarthrosis  (joints  mixed) — example,  Isis,  Gorgonia,  Pen- 
tacrinus,  articulation  of  bodies  of  vertebrae  in  Mammalia. 

Diarthrosis  (synovial  joints). 

Arthrodia  (sliding  joint) — example,  symphysis  pubis  of 
human  pelvis. 

Enarthrosis  (ball-and-socket  joint) — example,  vertebrae  of 
Ophidia;  occipito-atloid,  articulation  of  Lepidosteus  (garpike); 
spines  of  Echinodermata. 

Ginglimus  (hinge  joint) — example,  articulates  generally. 
Here  the  movement  between  member  of  a  limb  is  lateral, 
excepting  Acoetes  lupina,  where  it  is  vertical:  hinge  joint  of 
bivalve  shells,  tempora-maxillary  joint  of  mammalia. 

Peculiar  apparatuses.  Spiral  valve  of  Brachiopoda,  pediculi 
and  ambulatory  apparatus  of  Toxopneustes  (sea  urchin) ;  pec- 
toral fin  of  Pimdodus  (catfish);  structure  of  joints  in  extremi- 
ties of  birds;  hock  joint  of  horse;  hip  joint  of  Phoca  (seal); 
and  tibio-astragaloid  articulation  of  certain  Dinosaurian 
reptiles. 


36  COMPARATIVE  ANATOMY. 

V. 

APPAKATUS  OF  MOTION, 

THE  movements  of  animals  are  effected  by  sarcodous  or 
ciliary  action. 

SAKCODOUS  ACTION.  Due  either  to  presence  of  sarcode  or 
muscular  tissue. 

Sarcode. — This  is  a  gelatinous,  diaphanous,  contractile 
substance,  occurring  abundantly  in  larvse  of  insects,  embryos 
of  vertebrates,  worms  and  radiates.  (Griffith,  Micrograph. 
Diet.) 

It  constitutes  nearly  the  entire  body  in  the  Rhizopoda; 
and  with  them  carries  on  all  the  nutritive  processes.  With 
such  its  contractility  enables  it  to  modify,  from  time  to 
time,  the  form  of  the  animal.  Thus  in  the  Amceba,  from 
the  alternating  contraction  and  dilatation  of  portions  of  the 
sarcode,  the  shape  of  the  animal  is  constantly  varying. 

Progression  is  effected  by  the  protrusion  of  portions  of  the 
sarcodous  mass  from  the  sides  of  the  organism,  forming 
foot-like  processes  (pseudo-podia).  These  may  be  made  to 
adhere  to  some  adjacent  object,  and  the  body  slowly  drawn 
toward  the  point  of  attachment.  Under  certain  circum- 
stances Amdba  protrudes  its  pseudo-podia  at  one  extremity 
of  the  animal  immediately  in  advance  of  the  contractile 
vesicle. 

The  motion  of  an  embryonic  mass  within  its  egg  capsule 
before  any  differentiation  of  tissue  is  seen,  is  perhaps  com- 
parable to  that  of  sarcode. 

Muscular  Tissue. — This  is  a  peculiar  contractile  substance 
resembling  sarcode,  arranged  within  tubular  sheaths.  A 
single  sheath  with  contents  constitutes  a  fibrilla,  a  collection 
of  fibrillse,  a  fibre,  and  a  bundle  of  fibres,  a  muscle. 

The  primary  elements  of  muscular  tissue  in  a  state  of  de- 
composition possess  independent  motion.  (Clark.) 

Every  muscle  being  in  relation  to  one  or  more  movable 


APPARATUS   OF   MOTION.  37 

points,  motion  of  such  points  results  when  the  muscular  axis 
is  shortened. 

Muscles  are  divided  into  the  striated  (when  the  tubular 
contents  of  each  sheath  are  transversely  divided  into  disks) 
and  the  non-striated  (when  such  division  is  absent).  The 
muscles  are  striated  in  Salpa  and  certain  Polyzoa; — Crusta- 
cea, Arachnida,  Insecta  (with  whom  it  is  seen  in  both  volun- 
tary and  involuntary  muscles) ;  and  Yertebrata,  with  whom 
it  is  confined  to  the  voluntary  muscles  and  heart.  They 
are  non-striated  in  Radiata,  Entozoa,  and  Annelida;  Lamel- 
libranchiata  generally,  Gasteropoda,  Cephalopoda,  and  in 
the  majority  of  the  involuntary  muscles  of  Vertebrata. 

Muscles  are  white  in  Invertebrata,*  Pisces,  Batrachia,  and 
Reptilia.  Exception,  Salmo  (salmon),  Adpenser  (sturgeon), 
Squalus  "(shark),  where  they  are  red.  Constantly  red  in 
Aves  and  Mammalia,  excepting  pectoral  muscles  of  certain 
granivorous  birds,  as  Perdix  (partridge),  Phasianus  (pheas- 
ant), Gallus  (common  fowl).  This  change  of  color  is  asserted 
to  be  a  result  of  fatty  degeneration  of  muscular  fibre,  from 
want  of  use,-— a  view,  in  a  measure,  confirmed  by  the  leg 
muscles  of  Struthio  (ostrich),  which,  ordinarily  red,  become 
white  when  the  animal  is  for  some  time  confined.  (Quekett.) 

Descriptions  of  special  muscles. — Adductor  muscles  of  bi- 
valve molluscs,  pectoral  muscle  of  birds.  Diaphragm  of 
mammals,  abdominal  muscles  of  reptiles  and  mammals; 
cremaster  muscle;  panniculus  carnosus  (platysma  myoides); 
muscles  of  external  ear.  Muscles  peculiarly  developed  in 
man  are  glutei  and  stern o-cleido-mastoideus. 

CILIARY  ACTION.  Due  to  the  presence  of  cilia  or  sper- 
matic filament. 

Cilia. — These  are  minute  processes  (homogeneous  fila- 
ments), placed  in  connection  with  a  basement  membrane, 
and  endowed  with  a  constant  vibratile  motion. 

In  Yertebrata,  cilia  are  attached  to  epithelial  membrane; 
but  in  other  animals,  and  in  certain  embryos,  they  clothe  the 
peripheral  surface  of  organism.  They  are  seen  in  all  ani- 

*  See  Appendix. 


38  COMPARATIVE   ANATOMY. 

mals  excepting  Cephalopoda,  Crustacea,  terrestrial  arthropod 
Articulata,  and  Pisces,  excepting  Amphioxus. 

Spermatic  filament. — (See  page  103.) 

Among  accessories  to  motion  are  erectile  and  elastic  tissue. 

Erectile  Tissue. — A  periodic  turgescence  and  collapse  of 
certain  tissues  (erectile)  by  alternate  excess  and  comparative 
absence  of  blood,  may  be  considered  a  source  of  motion,  as 
witnessed  in  the  power  of  accommodation  of  parts  of  eye  in 
fishes,  through  choroid  body;  and  probably  in  the  dilatation 
and  contraction  of  the  pupil  of  the  eye  of  Mammalia,  and  in 
the  erection  of  the  penis  of  animals  of  the  same  class. 

Elastic  Tissue. — This  restores  parts  to  their  original  posi- 
tion from  which  they  have  been  moved  by  muscular  action, 
as  by  nuchal  ligament  of  vertebrates ;  or  maintains  patulency 
of  vessels,  as  in  arteries ;  or  aids  to  sustain  the  weight  of  vary- 
ing bulks  of  tissues,  as  in  the  abdominal  muscles  of  animals 
with  large  paunches,  as  in  ElepJias  (elephant),  and  Rhinoceros. 

The  pedicle  of  Vorticella,  and  lassocells  of  Hydra  also 
probably  possess  the  property  of  elasticity. 


VI. 

TEETH, 

TEETH  are  those  sclerous  appendages  to  the  pre-assimilative 
portion  of  the  alimentary  canal  subservient  to  the  prehension 
or  trituration  of  food. 

They  may  be  calcareous,  siliceous,  corneous,  chitinous, 
or  dentinal.  In  Invertebrata,  the  basis  of  tooth  structure  is 
commonly  same  as  basis  of  skeleton,  and  is  either  developed 
in  the  same  manner,  as  in  the  majority  of  Articulata,  or  in  a 
special  sac,  as  in  tooth-bearing  Mollusca  and  Nemertes.  In 
Vertebrata,  the  dentinal  sac  is  constantly  present,  is  not 
seen  in  the  skeleton,  and  arises  from  a  formative  bulb. 

False  Teeth. — '  Hinge  teeth'  of  bivalve  molluscs,  as  Unio 


TEETH.  39 

(mussel);  'teeth'  around  margin  of  certain  univalve  molluscs, 
as  in  Nerita  pdoronta  (bleeding-tooth  shell). 

PROTOZOA.  For  the  most  part  without  teeth;  when  ali- 
mentary canal  is  not  denned,  form  of  jaw  simple,  as  in  Dys- 
teria. 

RADIATA.  Coelenterata  without  teeth.  With  some  Echino- 
dermata,  as  Toxopneustes  (sea-urchin),  the  dental  apparatus 
(Aristotle's  lantern)  is  very  complex.  Five  prismatic  seg- 
ments or  jaws  are  arranged  to  one  another  around  the  mouth 
(which  presents  inferiorly),  like  the  segments  of  an  orange.  A 
slender  tooth  extends  through  the  longitudinal  axis  of  each 
jaw,  its  basal  or  formative  portion  being  above,  and  its  free 
and  trenchant  portion  exposed  at  mouth.  The  jaws  are 
moved  upon  one  another  by  abductor,  adductor,  and  con- 
strictor muscles. 

MOLLUSCA.  No  teeth  below  Gasteropoda. — Here  teeth  hav- 
ing a  siliceous  and  chitinous  basis  are  placed  in  numerous 
rows  transversely  to  a  narrow  cartilage-like  band  (lingual 
ribbon),  running  along  the  floor  of  gullet.  Each  row  is  com- 
posed of  denticles  having  narrow  bases,  but  free,  scalloped 
edges.  The  apparatus  is  moved  to  and  fro  by  muscular  action 
upon  a  simple  curved  plate  (upper  jaw)  in  the  roof  of  gullet. 

Scissor-like  teeth  in  Tritonia.  Calcareous  plates  upon  walls 
of  stomach  (gastric  teeth),  in  Build  and  Aplysia. 

Many  Pteropoda  possess  two  horny,  dentigerous  jaws,  op- 
posing laterally ;  and  a  tongue  armed  with  booklets  directed 
backwards.  Simpler  form  in  Hyalea. 

Cephalopoda. — Dibranchiata  have  two  horny  beak-like 
processes  at  mouth. 

ARTICULATA.  Teeth  with  few  exceptions  move  laterally. 
Entozoa. — Commonly  none.  Gizzard-like  teeth  in  Oxyuris 
(thread-worm). 

Rotifera. — Chitinous  cesophageal  apparatus;  composed  of 
a  central  piece  with  lateral  jaws;  constantly  motile,  and  pro- 
trusile. 

Annelida. — With  many  the  pharynx  has  a  horny  masti- 
catory apparatus,  sometimes  of  a  very  complicated  structure, 
and  which,  when  the  pharynx  is  protruded,  often  extends 


40  COMPARATIVE   ANATOMY. 

beyond  it,  and  serves  as  a  prehensile  organ.  They  are  usu- 
ally curved  like  hooks,  and  denticulated  upon  their  concave 
sides.  They  vary  in  number  from  two  to  nine  pair;  when 
numerous  they  are  of  dissimilar  forms  with  the  same  indi- 
vidual. (Siebold.)  They  move  laterally  upon  each  other,  ex- 
cept in  Acoetes.  (Stimpson.)  Single  siliceous  tooth  of  Bor- 
lasia,  placed  in  median  line  of  head,  with  remote  formative 
sacs.  For  Hirudo  (leech),  see  page  159. 

The  parts  entering  into  the  construction  of  the  mouth  in 
arthropod  articulates,  excepting,  perhaps,  certain  Crustacea, 
are  as  follows,  named  from  above  downwards:  labrum  (upper 
lip),  mandibles  (first  pair  of  jaws),  maxillae  (second  pair  of 
jaws),  labium  (lower  lip),  with  ligula  (tongue).  The  palpi  are 
always  appendages  to  either  the  rn axillae  or  labium. 

Arachnida.  —  The  mandibles  (cheliceres)  move  horizon- 
tally in  Scorpionidae  (scorpions),  vertically  in  Araneidae  (spi- 
ders); maxillae  and  maxillary  palpi  more  or  less  pronounced, 
latter  in  male  spiders  employed  as  feelers,  and  in  generative 
act  (see  p.  116).  Ligula  present  in  Scorpionidae,  absent  in 
Araneidae.  Labium  generally  wanting;  in  Scorpionidae 
deeply  cleft;  labial  palp  large,  commonly  progressive,  used 
as  feet,  but  in  Thelyphonus  and  Phrynus  as  antennae.  (Wood.) 

Myriapoda. — Organs  arranged  upon  three  types  according 
as  animals  are  (1)  carnivorous,  (2)  herbivorous,  or  (3)  suctorial. 

(1)  In  Syngnatha  (centipedes  proper),  labrum  commonly 
large;   maxillae  robust;   maxillary  palpi  well  defined  with 
ligula  placed   between  their  bases.     Labium  rudimentary, 
but  labial  palpi  large.     Scutum  of  sub-cephalic  segment  or 
ring  transformed  into  a  broad  false  labium,  or  gular  plate, 
with  the  feet  transformed  into  powerful,  prehensile  organs, 
and  provided  with  poison  glands. 

(2)  In  Chilognatha  manucentia,  as  in  Julidae  (millipedes), 
between  a  massive  labrum  and  a  broad  opposing  gular  plate, 
robust  maxillae  are  inserted ;  other  organs  wanting.     (3)  In 
Chilognatha  sugentia  as  in  Octoglena,  organs  fused  to  form  a 
suctorial  tube.  (Wood.) 

Insecta. — Organs  arranged  upon  two  great  types — (1)  Man- 
ducatory, and  (2)  Suctorial. 


TEETH.  41 

(1)  Labrum  pronounced;  mandibles  two  hard,  generally 
robust  organs  each  composed  of  a  single  piece  and  commonly 
denticulate  upon  opposing  surfaces.  Maxillae  two  softer  op- 
posing organs,  furnished  with  palpi,  each  composed  of  one  to 
six  articles.  Labium,  a  single  inferior  piece,  furnished  with 
labial  palpi,  each  composed  of  from  one  to  four  articles. 
Ligula  placed  at  the  base  of  the  labium.  Includes  Cole- 
optera  (beetle),  Neuroptera  (dragon-fly),  Orthoptera  (grass- 
hopper).— (2)  The  suctorial  form  of  mouth  may  be  due  to 
the  labium  being  prolonged  into  a  grooved  proboscis,  with 
the  other  parts  of  the  mouth  appearing  as  setae  toward  its 
base,  as  in  Diptera  (fly);  or,  to  the  labium  preserving  the 
function  of  a  sheath  to  the  setiform  mandibles  and  max- 
illae, the  labrum  becoming  rudimentary,  as  in  Hemiptera 
(bug) ;  or,  the  labium  may  be  absent,  with  the  mandibles  ru- 
dimental,  while  the  maxillae  are  enormously  developed  into 
a  symmetrical  suctorial  canal,  furnished  at  base  with  small 
maxillary  palpi,  the  whole  coiled  and  protected  in  rest  by 
palpi  arising  from  labium,  as  in  Lepidoptera  (butterfly). 

Apparently  intermediate  between  these  two  types  appear 
the  organs  of  Hymenoptera  (bee),  in  which  the  maxillae  are 
mostly  elongate,  and  form  with  labium  a  kind  of  sucking 
proboscis;  at  the  same  time  the  mandibles  are  well  developed, 
but  are  used  more  for  cutting  and  gnawing  during  search  for 
food  than  in  its  preparation. 

Crustacea. — Jaws  when  present  are  modified  feet.  In 
Limulus  (king-crab),  the  feet  perform  function  of  jaws.  In 
Decapoda  (lobsters,  crabs,  etc.),  an  upper  lip,  an  upper  pair 
of  jaws,  furnished  with  palpi,  two  pairs  of  lower  jaws,  each 
with  a  palpus,  are  present. 

VERTEBRATA.  The  tooth  of  a  vertebrate  animal  consists 
of  a  cellular  and  tubular  basis  of  animal  matter,  containing 
earthy  particles,  a  fluid,  and  a  vascular  pulp.  (Owen.) 

The  basis  is  dentinal  in  typical  tooth;  corneous  in  certain 
modified  structures,  as  in  teeth  of  marsipobranchiate  fishes, 
in  Balcena  (whale-bone  whale),  and  Ornithorhynchus  (duck-bill). 

A  typical  tooth  possesses  a  central  dentinal  mass,  capped 
with  enamel,  and  surrounded  by  cementum.  Cementum 


^ 

TJHIVBRSIT7 


42  COMPARATIVE   ANATOMY. 

and   enamel  may  be,  and  often  are,  absent,  but  dentine 
never. 

Developed  within  grooves  npon  surface  of  mucous  mem- 
brane, the  primitive  papillae  may  remain  exposed,  as  in  Sela- 
chia  (sharks),  or  each  become  encapsuled  within  mucous 
membrane,  as  in  many  osseous  fishes.  When  erupted,  the 
teeth  are  seen  to  be  either  attached  to  mucous  membrane 
alone,  as  in  Pisces,  or  inserted  in  bony  grooves  (alveoli),  which 
may  be  continuous,  as  in  Reptilia,  or  divided  transversely  into 
sockets,  as  in  Mammalia. 

Teeth  vary  greatly  in  numbers  and  position.  As  a  rule,  it 
may  be  stated  that  animals  developing  large  numbers  of 
teeth  on  surfaces  remote  from  the  region  of  lips,  are  inferior 
to  those  erupting  smaller  numbers  and  restricting  their  site 
to  the  anterior  portion  and  sides  of  mouth. 

Teeth  wanting  in  Aves,  except  in  Archceopteryx.  Rarely 
absent  in  other  vertebrates,  as  in  Amphioxus  (lancelet),  Aci- 
penser  (sturgeon),  Chelonia,  Myrmecophaga  (ant-eater),  and 
Manis  (pangolin). 

Pisces. — In  cartilaginous  fishes,  teeth  numerous,  pointed, 
tesselated.  Teeth  confined  to  jaws  proper,  as  in  Selachia 
(sharks). — In  Osseous  fishes  teeth  variable  in  number  and 
form.  They  may  be  conical,  setiform,  villiform,  lobed, 
curved,  etc.  Placed  chiefly  upon  vomer,  palatine,  intermax- 
illary, hyoid,  pterygoid,  inferior  maxillary  bones,  and  bran- 
chial arches,  they  occasionally  appear  upon  superior  maxil- 
lary, basi-occipital  and  nasal  bones.  Attachment  in  fishes 
generally  ligamentous,  as  in  Selachia.  Dentinal  varieties, 
vitrio-dentine,  vaso-dentine,  and  osteo-dentine.  Scarus  (par- 
rot fish)  has  apparently  enamel  and  cementum  in  addition  to 
dentine. 

Batrachia.  —  Teeth  generally  simple,  as  in  Rana  (frog). 
Placed  commonly  on  vomer,  intermaxillary,  and  portions  of 
inferior  maxillary  bones.  Remarkable  form  of,  in  Laby- 
rinthodon.  In  tadpole,  horny  beaks  are  present. 

Reptilia. — Ophidia,  conical,  placed  on  pterygoids,  palatine, 
maxillary  bones.  Teeth-like  process  on  cervical  vertebras  in 
Dtirodon.  Peculiarity  of  construction  of  poison  fang;  the 


TEETH.  43 

tooth  is  curved  backwards,  forming  a  canal  along  posterior 
surface  of  tooth,  which  communicates  with  duct  from  poison 
gland.  In  Lacertilia,  Iguanodon  partially,  and  in  Alligator 
entirely  inserted  within  alveolar  groove.  Peculiarity  of 
Dicynodon,  in  which  there  is  but  a  single  large  tooth  on 
either  side  of  superior  maxillary  bone. 

Mammalia. — Teeth  confined  to  intermaxillary,  superior, 
and  inferior  maxillary  bones ;  each  is  enclosed  within  a  bony 
socket,  and  placed  in  a  single  series  immediately  behind  the 
lips;  and  are  the  only  teeth  in  Yertebrata  which  may  possess 
more  than  a  single  fang.  They  are  of  a  definite  number,  and 
appear  in  sets  (when  they  are  divided  into  two  series,  the 
deciduous  or  milk  teeth,  and  the  permanent  teeth),  as  in  the 
majority  of  mammals,  or  are  of  one  set  only,  as  in  Cetacea. 
The  deciduous  teeth  are  always  fewer  in  number  than  the 
permanent;  and  in  Marsupialia  are  confined  to  a  single  tooth 
(posterior  molar)  on  either  side  in  each  jaw.  (Flower.)  The 
deciduous  teeth  are  sometimes  lost  prior  to  maturity  (in 
utero  in  some  Rodentia),  or  oftener  at  a  comparatively  early 
period  after  birth. 

Teeth  are  divided  into  cutting  teeth  (incisors),  tearing 
teeth  (canines),  and  grinding  teeth  (molars),  and  always 
hold  fixed  relations  to  the  character  of  food.  Thus  the  pre- 
ponderance of  a  conical  form  indicates  a  carnivorous  habit. 
With  it,  the  canines  are  greatly  developed,  the  incisors, 
pointed;  the  molars  are  acutely  cusped,  and  present  sur- 
faces adapted,  in  opposition,  to  divide  the  food  by  a  scissor- 
like  motion.  In  extreme  carnivorous  forms,  the  molars  are 
rudimentary,  as  in  Felis  (cat),  or  are  absent,  as  in  Machairodus 
(sabre-toothed  tiger). — The  preponderance  of  a  grinding  form 
indicates  an  herbivorous  habit.  With  it,  the  molars,  always 
present,  are  large,  flat,  and  yield  either  a  tuberculated  sur- 
face, as  in  Ursus  (bear),  or  a  flattened,  uneven  one,  marked 
by  ridges  of  enamel,  as  in  Equus  (horse).  Every  molar  is  con- 
structed upon  a  common  plan.  The  dentinal  centre  is  capped 
superiorly  by  enamel,  and  the  whole  structure  then  sur- 
rounded by  a  cemental  membrane.  Both  enamel  and  ce- 
mental  membrane  follow  the  curvings  of  the  surface  of  the 


44  COMPARATIVE   ANATOMY. 

dentine.  The  newly  erupted  tooth,  therefore,  presents  a 
cemental  surface  for  mastication.  This  may  be  a  simple 
membrane  (membrane  of  Nasmyth)  as  in  man,  when  it  will 
soon  disappear,  and  the  enamel  at  once  become  the  opposing 
surface ;  or  it  may  contain  cementum  in  abundance.  In  the 
latter  case  its  gradual  disappearance  from  the  convexities  of 
the  grinding  surface  leaves  exposed  the  enamel  cusps.  These, 
after  a  longer  time,  will  in  like  manner  be  worn  through, 
and  expose  circumscribed  areas  of  dentine.  So  that  in  the 
molar  tooth  of  an  adult  herbivore,  as  in  Castor  (beaver),  or 
Eguus  (horse),  the  islands  of  dentine  are  encircled  by  en- 
amel, while  cementum  fills  up  the  depressions.  In  the  her- 
bivorous type,  the  canines  are  often  absent.  The  incisors  are 
absent  as  in  upper  jaw  of  Ruminantia,  or  very  largely  devel- 
oped, as  in  Eodentia. — In  the  latter  order  they  are  pecu- 
liar in  having  no  closed  fang,  but  in  remaining  open  and 
continuous  with  the  pulp.  The  tooth  is  therefore  always 
growing ;  a  definite  length  being  secured  by  the  constant  loss 
of  substance  by  attrition  at  the  crown.  A  rodentic  incisor 
is  covered  with  a  thick  layer  of  enamel  anteriorly,  a  thin 
layer  posteriorly ;  the  latter  wearing  away  more  rapidly  than 
the  former,  a  scalpriform  surface  is  always  presented. 


VII. 

DIGESTIVE  SYSTEM, 

THE  solids  and  fluids  taken  into  the  body  as  food  are  sub- 
jected to  a  process  called  digestion,  by  which  the  solid  por- 
tions are  reduced  to  a  fluid  state,  the  nutritive  particles 
separated  from  the  excrementitious,  and  the  whole  prepared 
to  become  blood,  skeleton,  muscle,  etc.  (Agassiz  and  Gould.) 

The  digestive  apparatus  is  composed  of  an  alimentary  canal 
and  appendages. 

PROTOZOA.   With  the  simplest  forms  of  life,  as  in  the  Ehizo- 


DIGESTIVE   SYSTEM.  45 

poda,  there  is  no  alimentary  canal.  The  substances  received 
as  food,  by  the  extensions  of  the  sarcodous  mass,  may  be  re- 
tained at  any  portion  of  the  organism  during  the  digestion  of 
its  nutritive  elements;  the  excreta  to  be  subsequently  thrown 
off  at  a  convenient  point. — With  certain  ciliated  Infusoria,  the 
digestive  system  is  wanting,  as  in  Trichomonas.  In  Paramedum 
the  food  enters  an  oral  opening,  and  is  passed  along  a  short 
gullet  to  the  interior  of  the  body,  where,  in  the  form  of  globu- 
lar masses,  it  is  digested.  The  ejecta  escape  by  the  mouth. 

RADIATA.  Ccelenterata.  —  Digestion  takes  place  within  a 
central  cavity. 

Polypi. — Cavity  simple,  as  in  Hydra,  or  divided  into  cham- 
bers by  longitudinal  plications  of  the  outer  wall,  as  in  Actinia. 
The  wall  of  the  cavity  may  be  separated  from  integument  by 
an  intervening  space  (perigastric),  which  is  commonly  trav- 
ersed from  within  outward  by  partitions  defining  a  number 
of  cells.  These  communicate  with  stomach  by  apertures 
closed  during  digestion,  but  which  subsequently  open  to 
allow  the  escape  of  the  chyle  into  the  perigastric  space.  In 
the  coralline  polyps  this  space  being  common  to  many  indi- 
viduals, chyle  may  be  conveyed  to  a  distance  from  the  cavity 
elaborating  it. 

Acalephse. — Cavity  large,  as  in  Beroe,  or  small,  as  in  Pleu- 
robranchia.  It  is  commonly  furnished  with  thickened  parti- 
tions, which  transform  the  chambers  into  tube-like  canals. 
The  oral  openings  are  often  prolonged  into  pendant  tenta- 
cles, which  in  Physalia  (Portuguese  man-of-war)  are  long  and 
numerous. 

Echmoderrnata. — The  digestive  apparatus  is  separated  as 
a  tube  or  sac,  having  a  distinct  oral  and  commonly  an  anal 
opening.  When  tubular,  it  is  simple,  enclosed  in  a  peritoneal 
covering,  and  longer  than  body,  as  in  Toxopneustes  (sea- 
urchin),  or  as  long  as  body,  as  in  Synapta.  When  sac-like, 
it  is  simple,  with  numerous  short  cseca  not  entering  rays, 
as  in  Opkiura,  or  with  cseca  extending  along  entire  length 
of  rays,  as  in  Asteracanthion  (star-fish).  The  stomach  is  sepa- 
rated into  two  chambers  by  a  circular  projecting  fold.  The 
first  of  these  is  the  true  stomach,  and  the  second  sends  off 


46  COMPARATIVE   ANATOMY. 

the  radial  cseca  (Siebold).  The  anus,  in  Echinodermata,  is 
placed  alongside  of  mouth  in  Pentacrinus  (sea- lily);  upon 
dorsum,  either  directly  opposite  mouth  in  Toxopneustes,  or  to 
one  side,  as  in  Spatangus ;  at  posterior  extremity,  as  in  Holo- 
thuria  (sea-cucumber) ;  or  it  may  be  absent,  as  in  Astropecten. 

Hepatic  secretion  formed  from  gastric  follicles. 

MOLLUSC  A.  Polyzoa. — The  mouth  is  surrounded  by  prom- 
inent ciliated,  protrusile  tentacles.  The  canal,  after  leaving 
a  muscular  stomach  (gizzard),  turns  once  upon  itself  to  open 
by  an  anus  near  the  mouth. 

Hepatic  secretion  formed  from  gastric  cells. 

Brachiopoda. — The  two  respiratory  arms  (q.  v.)  are  placed 
one  on  either  side  of  the  mouth.  The  canal  may  be  simple, 
as  in  Lingula,  or  with  stomach,  as  in  Terebratula.  Anus  lat- 
eral, hidden  between  lobes  of  mantle;  absent  in  Waldheimia. 

Tunicata. — The  oral  opening  at  base  of  respiratory  cham- 
ber (q.  v.).  From  this  point  the  canal,  after  commonly  ex- 
panding into  a  stomach,  curves  at  first  downward,  then 
upward,  to  terminate  within  the  cavity  of  the  mantle, — an 
excretory  chamber,  common  to  both  alimentary  and  genital 
apparatus,  conducting  thence  the  ejecta. 

Lamellibranchiata. — Mouth  placed  near  anterior  adductor 
muscle,  with  tentacular  flap  on  either  side.  Stomach  large, 
and  lined  with  papillae.  Intestine  often  convoluted  and  inti- 
mately associated  with  other  viscera.  The  rectum  commonly 
traverses  the  heart  (Ostrea,  oyster,  an  exception);  anus  upon 
dorsum  near  hinge  line,  and  behind  position  of  posterior 
adductor  muscle.  Liver  a  large  diffuse  organ  made  up  of 
distinct  acini. 

Gasteropoda. — Mouth  simple,  protrusile,  and  tooth -bearing. 
Gullet  muscular.  Stomach  present,  simple,  as  in  Helix  (snail) ; 
gizzard-like,  as  in  Limnceus;  compound,  as  in  Aplysia  (sea- 
hare)  ;  occasionally  armed  with  teeth  (q.  v.).  Intestine  con- 
voluted, terminating  upon  right  side,  near  respiratory  orifice. 
Salivary  glands  present,  placed  either  around  oesophagus  or 
stomach.  Hepatic  secretion  always  present;  rarely  secreted 
from  intestinal  cells  or  follicles,  but  as  a  rule  from  well- 
developed,  lobulated  liver,  emptying  by  excretory  ducts  into 


DIGESTIVE  SYSTEM.  47 

stomach,  as  in  Helix  (snail),  intestine,  as  in  Lymnceus,  rarely 
in  oesophagus,  or  partially  externally,  as  in  Doris. 

Pteropoda. — Mouth  furnished  with  sucker-bearing  tenta- 
cles. In  other  respects  the  canal  closely  resembles  that  of 
Gasteropoda.  Hepatic  secretion  from  gastric  follicles,  as  in 
Clio.  Salivary  glands  pour  secretion  into  mouth. 

Cephalopoda. — Mouth  surrounded  by  prehensile  sucker- 
bearing  tentacles,  and  a  circular  fold  of  skin  which  is  serrated 
at  free  edge.  The  parrot-like  jaws  encompass  the  opening 
leading  into  a  muscular  pharynx,  which  is  furnished  with  a 
tongue  upon  its  floor.  Gullet,  well  defined,  and  extends 
thence  to  a  stomach,  which  is  generally  simple,  and  lined 
with  a  mucous  membrane  thrown  into  longitudinal  folds, 
covered  with  horny  epithelium.  In  Nautilus  a  crop  precedes 
the  muscular  stomach  or  gizzard.  The  intestine  is  narrow 
and  convoluted,  and  terminates  in  an  anus  within  the  mantle 
upon  the  right  side  of  body.  Appended  to  the  pyloric  ex- 
tremity of  the  stomach,  in  many  Cephalopoda,  is  a  globular 
or  spiral  viscus,  which  secretes  a  fluid  held  to  be  analogous 
to  the  pancreatic  fluid  of  the  Vertebrata.  Salivary  glands 
well  developed,  generally  two  pairs,  opening  into  gullet  near 
base  of  tongue  by  long  excretory  ducts.  Hepatic  secretion 
from  well-developed  liver,  which  commonly  surrounds  the 
oesophagus,  the  bile-duct  opening  into  intestine  at  region  of 
pyloric  appendage. 

ARTICULATA.  As  a  rule,  the  alimentary  canal  begins  upon 
the  dorsal  aspect  of  the  cranial  segments  and  terminates 
upon  the  ventral  aspect  of  the  terminal  caudal  segment. 

Rotifera. — The  mouth  is  simple  and  placed  between  the 
ciliated  disks.  The  armature  of  teeth  (q.  v.)  succeeds  to  a 
protrusile  gullet  emptying  into  a  thick,  simple  stomach. 
From  this  passes  a  narrow  intestine,  either  curved  upon  it- 
self, as  in  Melicerta,  to  terminate  upon  the  side,  or,  more 
straight,  to  open  at  caudal  extremity,  as  in  Rotifer. 

Two  csecal  appendages  to  stomach  secrete  a  colorless  fluid, 
perhaps  analogous  to  a  pancreatic  product.  A  hepatic  secre- 
tion is  derived  from  gastric  cells. 

Annelida. — The  mouth  is  usually  surrounded  with  thick 


48  COMPARATIVE  ANATOMY. 

lips,  with  tactile  appendages,  as  in  Serpula.  The  canal  is 
placed  in  the  axis  of  the  body,  having  no  convolutions,  as  in 
Lumbricus  (earth-worm),  or  possessing  them,  as  in  Sipunculus. 
It  may  be  comparatively  a  simple  tube,  as  in  Lumbricus, 
though  frequently  sacculated,  as  in  Hirudo,  leech  (q.  v.). 
Anus  dorsal.  Walls  of  canal  are  very  muscular,  a  free  peri- 
staltic motion  commonly  present. 

Glandular  appendages  in  the  form  of  follicles  surrounding 
the  commencement  of  the  intestine,  as  in  Sangitisuga,  or  a 
defined  gland  emptying  into  the  pharynx,  as  in  Lumbricus, 
a  secretion  analogous  to  saliva.  A  hepatic  secretion,  con- 
stantly present,  is  elaborated  from  simple  cells  aggregated 
upon  the  walls  of  the  intestinal  tube. 

Crustacea.  —  Mouth  with  numerous  appendages.  (See 
Teeth.)  Stomach  is  a  simple  dilation,  possessing  a  crushing 
apparatus  which  is  either  simple,  as  in  Limulus  (king-crab), 
or  complicated  and  composed  of  three  denticulated  chitinous 
pieces,  which  are  moved  upon  one  another  by  the  muscular 
coat  of  the  stomach,  to  crush  any  intervening  substances,  as 
in  Homarus  (lobster).  Intestine  extends  along  the  axis  of  the 
body  without  convolutions,  and  narrows  as  it  terminates  at 
the  anus. 

Salivary  secretion  rarely  present,  as  in  Lepas  (barnacle). 
Hepatic  secretion  is  poured  into  the  canal  from  simple  fol- 
licles at  varying  points,  as  in  Daphnia.  With  the  higher 
forms  a  liver  is  observed,  having  a  distinct  duct,  as  in 
Homarus. 

Myriapoda. — Stomach  rather  long  and  intestine  simple. 
Salivary  glands  generally  in  two  pairs  on  either  side  of  the 
oesophagus  and  stomach,  opening  into  mouth. 

Arachnida. — Intestine  may  be  simple,  extending  without 
any  divarication  to  anus,  as  in  Buthus  (scorpion),  or  with 
diverging  caeca,  as  in  Epeira.  These  may  extend  into  the 
feet  (phlebenterism),  as  in  Galeodes;  the  terminal  portions  of 
the  cseca  communicating  with  the  circulatory  system,  direct 
transmission  of  chyle  into  the  circulatory  fluid  is  secured. 
Termination  of  canal  at  end  of  oesophagus,  allowing  the  fluid 
food  to  pass  from  this  point  directly  into  the  soft  parts, of  the 


DIGESTIVE    SYSTEM.  49 

body,  as  in  Gamasus.     Anus  generally  terminal,  rarely  in 
middle  of  ventral  surface  of  abdomen,  as  in  Acarus. 

Salivary  secretion  universally  present.  Hepatic  secretion 
from  follicles  either  simple,  as  in  Trombidhan,  or  multiramose, 
as  in  Epeira. 

Insecta. — Intestine  can  be  divided  into  gullet,  crop,  giz- 
zard, small  intestine,  large  intestine,  and  rectum.  Anus 
terminal.  Great  variation  among  different  orders  of  insects 
with  respect  to  the  form  and  length  of  the  canal.  Coleop- 
tera  have  crop,  followed  often  by  an  ovoid  gizzard.  The 
small  intestine  is  often  longer  and  more  convoluted  in  the  car- 
nivorous than  in  the  herbivorous  families.  Orthoptera  have 
gizzard  armed  with  rows  of  horny  denticulated  plates.  Hym- 
enoptera,  with  simple,  thin,  and  dilated  sucking  stomach. 
Hemiptera,  with  compound  stomach,  consisting  of  two  or 
three  chambers.  Diptera,  with  sucking  stomach,  commonly 
pedunculated. 

Salivary  secretion  elaborated  in  csecal  tubes,  sometimes  of 
great  length,  which  open  into  the  oral  cavity.  Hepatic  secre- 
tion from  gastric  cells,  or  long  simple  caeca.  A  fluid,  analo- 
gous to  the  pancreatic  secretion,  flows  from  follicles  appended 
to  the  small  intestine.  —  The  connection  we  find  existing  be- 
tween the  alimentary  canal  and  food  of  Yertebrata — the  for- 
mer being  simple  when  the  food  is  simple,  complicated  when 
much  preparation  is  required  of  the  food — does  not  subsist 
to  the  same  degree  among  insects.  Thus  the  Tenebrionidse, 
which  subsist  on  wood,  have  a  comparatively  simple  canal, 
while  Lepidopterous  insects,  living  on  honey,  have  a  much 
more  complicated  one. 

YERTEBRATA.  Pisces. — Gullet  short,  wide,  and  ends  in 
stomach  by  a  slight  constriction;  regurgitation  readily 
effected.  Long  fleshy  processes  from  the  mucous  membrane 
project  backward  as  in  Selachia  (sharks).  Stomach  gen- 
erally simple.  Gizzard-like  structure  in  Salmofurio  (Gillaroo 
trout).  Intestine  short,  with  few  exceptions.  Convoluted 
in  a  few  Cyprinoids,  rarely  coiled  around  the  air  bladder 
(Campostoma).  Anus  commonly  directly  in  advance  of  anal 
fin.  Except  Gymnotus  (electric  eel),  and  Apliredoderus,  where 

4 


50  COMPARATIVE   ANATOMY. 

it  is  placed  more  anteriorly.  Intestine  spiral  as  in  Mustela 
(dogfish),  convoluted,  as  in  Zygoma  (hammer-beaded  shark); 
terminates  in  anus  without  colon  or  caecum.  Liver  large, 
oily,  soft,  lobular;  gall-bladder  present;  duct  terminates  in 
duodenum  near  pylorus. 

Pyloric  caeca  to  stomach,  as  in  Gadus  (cod),  furnish  a  pan- 
creatic secretion. 

Batrachia. — Tongue  broad,  flat,  and  attached  anteriorly 
to  margin  of  lower  jaw,  with  free  part  lying  behind;  gullet 
short;  stomach  simple  and  intestine  but  little  convoluted ; 
rectum  terminating  in  cloaca.  In  tadpole  the  intestine  is 
longer  and  more  convoluted  than  in  frog.  Liver  with  gall- 
bladder; salivary  glands  often  wanting;  pancreas  present. 

Reptilia. — Tongue  of  various  forms.  In  Chelonia  covered 
with  papillae ;  long,  slender,  and  protrusile  in  Chameleo  (cha- 
meleon). Gullet  long,  without  crop.  In  Chelonia,  furnished 
with  papillae  or  horny  processes.  In  Ophidia,  sometimes  more 
capacious  than  stomach.  Stomach  simple.  In  Crocodilia,  giz- 
zard-like. In  Ophidia  the  stomach  is  small,  merging  insen- 
sibly into  gullet.  Generally  possesses  thick,  muscular  walls 
with  marked  pyloric  constriction.  Intestine  divisible  into 
large  and  small;  frequently  with  plicated  mucous  membrane 
as  in  Ophidia,  thrown  into  zigzag  folds  as  in  Crocodilia; 
caecum  rarely  present  except  in  Sauria.  It  always  terminates 
in  a  cloaca.  Liver  divided  into  two  or  more  lobes;  gall-blad- 
der present,  either  embedded  in  organ  (Amphisbcena)  or  remote 
from  it  (Ophidia) ;  salivary  and  pancreatic  glands  generally 
present. 

Aves. — Oral  pouches  in  Pdicanus  (pelican);  oesophageal  in 
Otis  (bustard).  Crop  (ingluvies)  usually  on  right  side  of  neck 
in  front  of  clavicles  (furcula);  in  Columba  (pigeon),  one  on 
either  side,  and  is  often  furnished  with  numerous  and  varied 
glands.  Power  of  regurgitation  of  the  contents  of  crop  pos- 
sessed by  some  birds,  as  Columba.  Crop  absent  in  Anser 
(goose),  and  Cygnus  (swan).  Stomach  divided  into  two  parts. 
First,  cardiac  or  glandular  (proventriculus).  This  furnishes 
the  true  gastric  secretion;  its  glands  are  of  a  variety  of  shapes. 
Second,  pyloric,  muscular  (gigerium,  gizzard).  The  walls  are 


DIGESTIVE    SYSTEM.  51 

much  thicker  than  in  the  other  chamber — moderately  so  in 
rapacious — markedly  so  in  granivorous  birds.  In  the  latter 
the  epithelium  forms  two  thick  plates  for  the  trituration  or 
food.  Hairy  concretions  found  in  gizzard  of  Cuculus  (cuckoo). 
Intestine  small  and  large, — small,  folded  several  times  upon 
itself;  large,  straight,  with  commonly  two  caeca,  one  on 
either  side;  terminates  in  a  cloaca. 

Salivary  glands  present:  pancreas  generally  with  more 
than  a  single  duct.  Liver  almost  always  divided  into  two 
lobes;  gall  bladder  wanting  in  few  birds. 

Mammalia. — Gullet  narrow,  with  thick  walls.  Stomach 
either  simple,  constricted,  sacculated,  or  compound.  Simple 
in  Carnivora  and  man,  when  it  is  pyriform,  the  base  being  at 
cardiac,  and  apex  at  pyloric  end ;  constricted  in  Equus  (horse), 
defining  cardiac  from  pyloric  extremity;  sacculated  in  Pho- 
ccena  (porpoise),  and  Rodentia,  where  the  constriction  is  car- 
ried so  far  as  nearly  to  divide  the  stomach  into  distinct  cham- 
bers. Such  division  is  actually  attained  in  Pteropus  (frugivo- 
rous  bat),  in  which  two,  and  in  Macropus  (kangaroo),  and 
Semnopithecus  (douc  monkey),  with  whom  three  divisions  are 
seen,  each  of  which  in  their  turn  may  possess  a  tendency  to 
sacculation, — the  last  constriction  recalling  the  form  of  large 
intestine.  In  Ruminantia  the  stomach  is  compound  and 
divided  into  four  peculiar  chambers.  First,  paunch  (rumen), 
much  larger  than  the  others,  with  thin  walls,  and  furnished 
upon  its  inner  surface  with  horny  papillae;  second,  honey- 
comb (reticulum,  'hood'),  smaller,  lies  on  the  right  of  pre- 
ceding and  is  lined  with  deep  four-,  five-,  or  six-sided  cells; 
third,  many-plies  (psalterium,  omasum,  'book'),  the  smallest, 
is  of  a  sub-globular  form,  and  furnished  with  a  number  of 
deep,  longitudinal  lamellae  of  mucous  membrane,  which  are 
closely  approximated :  fourth,  the  true  stomach  (abomasum, 
'reed'),  which  resembles  in  form  the  human  stomach;  the 
mucous  membrane  is  sparsely  plicated  longitudinally.  With 
the  Camelidae,  the  many-plies  is  wanting,  and  the  paunch  is 
without  papillae,  while  a  reticulated  structure  resembling 
that  of  the  honeycomb  is  seen  at  its  fundus. 

Peculiar  gastric  gland  met  with  in  Phascolomys  (wombat) 
and  Rodentia. 


52  COMPARATIVE   ANATOMY. 

Small  intestine  long,  of  greater  extent  in  herbivorous  than 
carnivorous  animals;  villi  present;  numerous  filiform,  villi- 
bearing  process  in  Rhinoceros.  N~'O  valvulse  conniventes  in 
Carnivora.  Csecum  small  and  simple  in  carnivorous,  large 
or  compound  in  herbivorous  mammals,  as  in  Ruminantia 
and  Rodentia.  Furnished  with  two  simple  cseca  as  in  Myr- 
mecopJiaga  (ant-eater),  or  with  single  bifurcated  spiral  ap- 
pendage, as  in  Hyrax  (cony).  Vermiform  appendix  is  the 
rudiment  of  csecum ;  seen  only  in  Phascolomys  (wombat), 
anthropoid  apes  and  man. 

Salivary  glands  not  present  in  Cetacea.  Pancreas  always 
present,  commonly  divided  into  two  lobes.  Liver  divided 
into  many  lobes  in  the  Carnivora.  It  is  small  and  but  little 
divided  in  those  having  a  compound  stomach.  The  liver  of 
Quadrumana  closely  resembles  that  of  man.  Gall-bladder 
generally  present;  absent  in  Equus  (horse),  Elephas  (elephant), 
and  carnivorous  Cetacea;  double  in  Giraffa  (giraffe).  Bile 
may  flow  directly  into  the  gall-bladder,  as  in  the  ox;  but  com- 
monly the  hepatic  duct  is  joined  by  the  cystic  duct  forming 
the  ductus  communis,  as  in  man. — Adventitious  intestinal 
products  occasionally  met  with,  such  are  tappen,  from  bear, 
during  hybernation;  ambergris  from  whale;  bezoars  from 
goat  and  deer;  phosphatic  and  calcareous  calculi  from  horse; 
felt-balls  from  paunch,  and  occasionally  'honeycomb'  of 
ox,  etc. 


VIII. 

CIEOULATOEY  AND  EESPIEATOEY  SYSTEMS, 

CIRCULATION  is  the  movement  of  nutritive  fluids  of  animals 
in  fixed  directions,  and,  for  the  most  part,  within  a  peculiar 
apparatus. 

The  object  of  a  circulation  is  twofold — 

(1)  To  convey  from  an  assimilative  surface  nutritive  ele- 
ments, and  distribute  them  through  the  tissues. 


CIRCULATORY   AND    RESPIRATORY   SYSTEMS.  53 

(2)  To  bring  blood  in  contact  with  aerating  and  excretory 
organs. 

(1)  No  circulation  is  found  in  the  simplest  organisms;  for 
at  different  times  every  portion  of  the  common  tissue  comes 
in  contact  with  fresh  ingesta.  But  where  parts  are  devel- 
oped at  points  remote  from  a  more  or  less  defined  alimentary 
canal,  means  for  the  transmission  of  a  nutritive  fluid  (blood) 
from  central  to  peripheral  areas  become  necessary.  This 
fluid  may  enter  the  system  directly  or  indirectly :  directly, 
through  openings  in  the  sides  of  the  stomach  into  an  irregu- 
lar perigastric  space,  as  in  most  Polypi,  or  by  mouths  of 
gastric  caeca  (phebenterism),  as  in  certain  Arachnida ;  indi- 
rectly, by  absorption  through  veins,  as  in  higher  Invertebrata, 
or  through  both  veins  and  lacteals,  as  in  Vertebrata. 

Blood,  thus  viewed  in  its  broadest  sense,  is  composed  of  a 
liquid  (liquor  sanguinis,  serum)  and  corpuscles. — The  liquor 
sanguinis  very  commonly  is  exclusively  the  product  of  the 
walls  of  the  blood-vessel  system;  but,  in  lowly  organized 
animals,  it  may  receive  accessions  from  without,  as  in  Ento- 
zoa  (q.  v.). — The  blood  corpuscles  are  minute  bodies,  floating 
in  the  liquor  sanguinis.  They  are  generally  rounded,  or  oval ; 
possessing  with  the  Invertebrata  an  uneven  or  obscurely  tu- 
berculated  surface,  and  faintly  granular,  and,  at  times,  nu- 
cleated contents.  The  shape  and  size  of  the  corpuscles  are 
tolerably  constant  in  the  blood  of  the  individual,  but  may 
markedly  vary  in  that  of  different  species.  With  Verte- 
brata, two  kinds  of  corpuscles  recognized:  the  white,  which 
corresponds  to  the  above,  and  the  red,  which  is  the  smaller 
and  more  numerous.  The  red  corpuscle,  subject  to  more 
variation  than  the  white,  may  be  round,  disciform  solid 
bodies,  as  in  marsipobranchiate  fishes,  and  man ;  oblong 
and  nucleated,  as  in  JRana  (frog) ;  oval  and  of  great  relative 
size,  as  in  Proteus  (salamander).  Their  numbers  hold  a  rela- 
tion to  the  natural  heat  of  the  animal ;  being  more  numerous 
in  Aves  than  in  Mammalia,  and  in  the  latter  than  in  Pisces. 

Blood  is  of  different  colors.  In  Yertebrata  it  is  red,  with 
exception  of  Amphioxus,  where  it  is  colorless.  Commonly 
colorless  with  Invertebrata,  it  may  be  greenish,  reddish,  or 


54  COMPARATIVE   ANATOMY. 

brownish,  as  in  Acalephse;  yellowish,  greenish,  or  red,  as  in 
Annelida ;  or  blue,  as  in  Crustacea.  The  hue  is  generally 
resident  within  the  corpuscles;  but  occasionally,  as  in  certain 
Annelida,  is  contained  within  the  serum. 

Vascular  currents  are  maintained  by  ciliary  or  muscular 
action.  The  latter  may  be  secured  everywhere  in  the  con- 
tractile walls  of  the  vessels,  as  in  Annelida,  or  located  in 
specialized  portions  (pulsatile  vesicles,  or  'hearts'),  as  in  the 
majority  of  the  higher  forms. 

Systems  of  blood-vessels  may  be  complete  when  the  arte- 
ries and  veins  unite  through  an  intermediate  network  of 
small  vessels  (capillaries),  as  in  most  Annelida  and  Verte- 
brata;  or  incomplete,  when,  in  place  of  the  capillary  vessels, 
spaces  (lacunae),  irregularly  limited  by  muscles  and  viscera 
intervene,  as  in  Mollusca. 

(2)  Where  no  circulation  is  present,  the  interchange  of 
gases  takes  place  in  all  parts  of  the  animal  (aeration).  But 
where  one  exists,  a  separate  apparatus  is  devoted  to  the  reno- 
vating function,  which  is  then  called  respiration.  Aeration, 
however,  may  occur  in  conjunction  with  respiration,  as  in 
intestine  of  Cobitis  (loach),  and  dorsal  integument  of  Rana 
(frog).* 

The  respiratory  apparatus  is  subject  to  great  variation  in 
form  and  position.  The  plans  of  construction  are  dependent 
upon  the  type  to  which  the  animal  conforms,  and  the  nature 
of  the  medium  in  which  it  lives.  This  last  may  be  (1)  Nutri- 
tive Juices:  examples  include  embryos  of  viviparous  animals, 
as  in  Paludina  (fresh-water  snail),  Anableps,  Blennius,  Selachia, 
and  Mammalia.  (2)  Water  containing  air:  examples  include 
Pisces,  young  Batrachia,  and  all  oviparous  Invertebrata,  ex- 
cluding pulmonate  Gasteropoda,  and  certain  Articulata,  as 
pulmonate  Arachnida,  and  some  larval  forms  of  Insecta. 
(3)  Air :  examples  include  eggs  of  Reptilia  and  Aves,  adult 
Batrachia,  Reptilia,  Aves  and  Mammalia,  and  those  excepted 
in  the  preceding  enumeration. 

The  aerating  medium  may  be  taken  to  the  blood,  entering 

*  For  excretory  fuuctiou,  see  p.  64. 


CIRCULATORY  AND    RESPIRATORY    SYSTEMS.  55 

and  traversing  the  body  for  this  purpose,  either  through  a 
water-vascular  system  (q.  v.),  or  through  a  system  of  tracheal 
tubes,  as  in  Myriapoda,  Insecta,  and  certain  Arachnida.  Or  the 
blood  maybe  brought  to  the  medium,  either  through  agency 
of  (1)  vascular  processes  (branchiae),  or  (2)  lungs. — (1)  When 
the  former,  they  may  be  suspended  in  the  water,  as  in  Pisces, 
the  aquatic  Mollusca,  most  Annelida,  Crustacea,  all  larval 
and  a  few  adult  forms  of  Batrachia;  or  be  inverted,  forming 
a  branching  tube,  as  in  Holothuria  (sea  cucumber).  (2)  When 
the  latter,  special  air  sacs  are  developed,  which  may  be  simple 
pneumonic  chambers,  as  in  terrestrial  Gasteropoda,  and  pul- 
monate  Arachnida,  or  lobulated,  generally  symmetrical  sacs, 
opening  by  tubes  (bronchi)  into  a  single  passage  (trachea),  as 
in  all  air-breathing  Vertebrata. 

Many  aquatic  invertebrates  have,  in  addition  to  a  true  cir- 
culatory system,  or,  with  some,  apparently  taking  its  place, 
means  of  introducing  and  retaining  within  their  tissues, 
quantities  of  water.  The  fluid,  which  may  be  considered  as 
analogous  to  the  serum  of  the  blood,  passes  in  and  out  of  the 
body,  through  appropriate  openings  which  lead  within  to 
more  or  less  defined  expressions  of  communicating  vessels, 
or  lacunae.  While  within  the  body  it  may  become  admixed 
with  corpuscles,  and  is  doubtless  subservient  to  nutritive  and 
excretory  processes.  Such  is  the  fluid  of  the  aquiferous  sys- 
tem of  Acalephse;  the  perigastric  space  and  pediculi  of  Echi- 
nodermata;  the  'atrial'  system  of  Brachiopoda  and  Tunicata; 
the  aquiferous  system  in  certain  Lamellibranchiata  and  Gas- 
teropoda ;  the  water-vascular  system  (q.  v.),  etc. 

PROTOZOA.  Infusoria. — The  '  contractile  vesicle '  appears  to 
represent  a  rudimentary  circulatory  system.  In  Paramecium 
two  vesicles  are  present,  which  alternately  contract  and 
dilate.  The  site  of  each  vesicle  is  found  upon  contraction 
to  be  associated  with  a  number  of  canals  arranged  in  a 
radiate  manner  to  a  central  point.* 

*  Both  vesicles  lie  close  to  the  wall  of  the  body  on  the  side  nearly  oppo- 
site to  that  on  which  the  mouth  opens.  When  expanded  each  vesicle  is 


56  COMPAKATIVE   ANATOMY. 

EADIATA.  Coelenterata. — With  some  Polypi  closed  blood- 
vessels exist  upon  both  sides  of  the  body  and  stomach :  they 
have  proper  walls,  and  circulate  a  fluid  containing  a  great 
number  of  white  globules.  (Siebold.)  Acalephse. — Without 
proper  sanguineous  system.  The  so-called  vessels  would 
appear  to  be  ramified  and  anastomosing  gastric  tubules.  An 
'aquiferous  system'  is  announced  in  the  form  of  ciliated 
canals  traversing  the  body  and  receiving  water  through 
stomach,  or  directly  from  without,  to  be  ejected  through 
openings  upon  the  extremity  of  the  body  and  on  the  margin 
of  the  disk  (Ibid.).  —  The  Crelenterata  are  without  a  dis- 
tinctive respiratory  apparatus. 

Echinodermata. — Blood-vessel  system  complete.  Its  gen- 
eral expression  is  a  circular  vessel  surrounding  the  mouth 
and  anus,  communicating  with  rudimentary  hearts  and  pos- 
sessed of  diverging  arterial  and  venous  branches.  Heart 
absent  in  Holothuria.  In  Asteracanthion  (star-fish)  and  Ophiura, 
water  passes  freely  through  openings  in  the  skeleton,  the 
currents  among  the  viscera  being  determined  by  cilia.  This, 
the  aquiferous  system,  performs  in  part  the  function  of  res- 
piration. With  others,  internal  branchiae  extend  upward 
among  viscera  to  assume  an  arborescent  form  (respiratory 
tree),  as  in  Holothuria  (sea-cucumber):  a  smaller  and  more 
tentacular  form  is  seen  in  Echiurus. 

MOLLUSCA.  Blood-vessel  system  incomplete;  heart,  with 
the  exception  of  Cephalopoda,  systemic,  i.  e.  one  that  receives 
the  aerated  blood  from  gills  to  distribute  it  through  the  body. 
Currents  of  water  over  branchial  surfaces  induced  by  ciliary 
action,  except  in  Cephalopoda. 

Polyzoa. — Respiration  effected  through  tentacles  surround- 
ing mouth. 

about  half  as  broad  as  body.  Upon  contraction  occurring,  the  radiated 
canals  appear  as  fine  streaks,  which  gradually  broaden  as  the  main  portion 
lessens,  until  the  former  is  emptied,  and  nearly  invisible.  As  the  main 
vesicle  begins  to  expand,  the  canals,  in  nearly  regular  sequence,  suddenly 
open  and  their  contents  pour  into  the  central  chamber.  They  then  gradu- 
ally disappear  while  the  vesicle  again  contracts.  (Clark.) 


CIRCULATORY  AND   RESPIRATORY   SYSTEMS.  57 

Brachiopoda. — Hearts  two,  one  on  either  side  the  ali- 
mentary canal.  Respiration  by  two  long  spiral  branchise. 

Tunicata. — In  Salpa,  two  vascular  trunks  are  placed  on 
either  side  of  mantle,  upon  the  inner  side  of  which  extend 
the  branchise.  With  Ascidians,  a  heart  of  a  single  cavity  is 
placed  at  lower  part  of  body.  The  circulation  of  blood  is  to 
and  fro.  Branchial  chamber  at  the  same  time  a  pharynx. 

Lamellibranchiata. — Heart  is  simple  with  some,  but  may 
contain  both  auricle  and  ventricle.  Occasionally,  as  in 
Area,  a  distinct  heart  is  placed  upon  either  side  of  the  body. 
It  is  generally  pierced  by  rectum,  Ostrea  (oyster)  an  excep- 
tion. There  are  two  pair  of  branchise,  which  as  four  lamellae, 
embrace  either  side  of  the  abdomen  and  foot.  Each  lamella 
is  formed  by  a  widely-projecting  cutaneous  fold,  the  two 
leaves  of  which  are  connected  by  numerous  transverse  septa, 
to  which  correspond  externally  as  many  furrows,  passing 
from  the  base  of  each  branchia  to  its  borders. 

Gasteropoda. — Heart  composed  of  two  chambers,  almost 
always  in  close  relation  with  the  respiratory  apparatus,  and 
often  pierced  by  rectum.  Respiration  mostly  by  branchise, 
occasionally  by  lung-like  structure.  The  branchial  appa- 
ratus varies  in  its  form,  and  may  be  situated  upon  different 
portions  of  the  body.  Thus,  the  gills  may  be  exposed  in 
tufts  upon  the  back,  as  in  Doris;  or  arranged  on  either  side 
of  the  body,  in  a  furrow  between  the  mantle  and  the  foot, 
transversely,  in  a  single  row,  as  in  Phyllidia;  or  composed  of 
divided  lamellse  resembling  divided  leaves,  as  in  Aplysia  (sea- 
hare)  ;  or  foliaceous,  or  pyramidal,  arranged  in  rows  on  either 
side  under  the  margin  of  mantle,  as  in  Chiton;  or  composed 
of  numerous  leavelets,  arranged  parallel,  like  the  teeth  of  a 
comb,  as  in  Paludina  (fresh-water  snail).  The  pneumonic 
apparatus  is  situated  upon  the  right  side  of  body,  opening 
externally  by  an  aperture  through  mantle,  and  furnished 
with  a  network  of  vessels  running  on  its  walls.  The  shell 
is  a  special  protector  to  the  respiratory  apparatus,  and  is 
placed  upon  it  even  when  rudimentary. 

Cephalopoda. — Heart  central,  of  two  cavities,  and  sur- 
rounded by  pericardium.  Those  forms  having  two  pairs 


58  COMPARATIVE   ANATOMY. 

of  branchiae  (Tetrabranchiata),  as  in  Nautilus,  receive  two 
branchial  veins ;  those  having  but  a  single  pair  (Dibranchi- 
ata),  as  in  Sepia  (cuttlefish),  receive  but  one.  At  the  base 
of  each  branchia  is  a  muscular  chamber,  termed  branchial 
heart,  which  transmits  venous  blood  to  the  branchiae.  The 
return  blood  passes  through  a  systemic  auricle  before  enter- 
ing the  ventricle,  thence  to  be  distributed  through  the  body. 
Currents  of  water  over  gill  surfaces  induced  by  muscular 
action  in  mantle. 

ARTICULATA.  Eotifera  and  Entozoa.  (See  water-vascular 
system,  p.  65.) 

Annelida. — Blood-vessel  system  complete.  Vessels  nu- 
merous. Many  arrangements  obtain  with  different  genera, 
the  general  plan  conforming  to  that  seen  in  all  the  higher 
articulates,  in  the  presence  of  longitudinal  vessels  extending 
the  whole  length  of  body.  As  a  rule,  a  dorsal  and  ventral 
canal  are  seen,  occasionally  combined  with  lateral  vessels, 
which  may  in  some  instances  communicate  with  a  vertical 
set  joining  the  other  two. — The  position  of  the  respiratory 
apparatus  determines  the  detail  of  the  blood-vessel  system. 
In  Lumbricus  (earthworm)  there  is  apparently  no  apparatus 
exclusively  devoted  to  respiration.  Respiratory  organs,  how- 
ever, generally  present.  These  may  be  arranged  in  depres- 
sions upon  cephalic  segments,  as  in  Nemertes;  within  the 
abdominal  cavity,  as  in  Hirudo  (leech),  q.  v.;  in  a  brilliantly- 
colored,  spiral  tuft  to  head,  as  in  Serpula;  or  symmetrically 
appended  to  the  dorsal  surface  of  each  segment,  as  in  Eunice. 

Crustacea. — Blood-vessel  system  incomplete.  Heart  of  a 
single  cavity  beneath  shell  at  anterior  part  of  the  body. 
Venous  currents  empty  into  a  dorsal  sinus  which  encloses 
the  heart.  Respiration  by  branchiae,  excepting  in  low  forms, 
as  in  Cyclops  and  Lerncea,  where  aeration  takes  place-  from 
the  cutaneous  surface.  Branchiae  may  be  free,  as  in  Lepas 
(barnacle);  or  enclosed,  as  in  Homarus  (lobster),  and  com- 
monly placed  at  the  base  of  the  anterior  true  or  false  feet. 
Constantly,  without  cilia,  currents  are  secured  by  muscular 
action  of  false  feet  and  appendages. 

Arachnida. — Blood-vessel  system  incomplete.    Heart  com- 


CIRCULATORY  AND   RESPIRATORY   SYSTEMS.  59 

monly  a  simple  dorsal  vessel.  Respiration  by  tracheae,  as  in 
Acarus  (mite),  or  by  lungs,  as  in  Epeira  (true  spider).  Aera- 
tion seen  in  Emydium  (water-bear). 

Insecta  and  Myriapoda. — Blood-vessel  system  incomplete. 
Dorsal  vessel,  or  heart,  articulated.  Venous  canals  com- 
municate in  a  dorsal  sinus.  Respiration  trachea!.  False 
tracheae  in  aquatic,  larval,  and  pupal  forms,  as  in  Ephemera 
(May -fly);  but  true  tracheae  in  all  adult  forms  of  Insecta. 

VERTEBRATA.  Blood-vessel  system  complete ;  hepatic  portal 
circulation  constant, — blood  contributed  to  it  from  tail  in 
Pisces,  and  from  tail  and  posterior  extremities  and  kid- 
neys in  certain  Batrachia  and  Ophidia.  Heart,  with  excep- 
tion of  Amphioxus  (lancelet),  of  more  than  a  single  cavity. 
Coloration  of  blood  due  to  presence  of  red  blood  corpuscles. 

Pisces. — The  venous  blood  is  conveyed  to  a  large  sinus 
near  pectoral  region.  Heart  composed  of  two  chambers, — a 
single  auricle  and  ventricle, — and  is  placed  at  the  junction  of 
head  and  trunk  above  the  position  of  coracoid  bones.  It 
contains  venous  blood  which  is  sent  through  branchiae  to  be 
returned  arterialized  to  the  aorta,  and  is  thence  distributed 
over  the  body:  it  is  thus  seen  to  be  a  branchial  heart  as  op- 
posed to  the  systemic  heart  of  lamellibranchiate  and  gas- 
teropod  molluscs.  The  commencement  of  the  aorta  is  fur- 
nished with  a  special  dilatation  (bulbus  arteriosus)  which  is 
rarely  absent,  as  in  marsipobranchiates,  and  Amphioxus.  In 
osseous  fishes  it  exhibits  a  single  row  of  valves ;  but  in  the 
cartilaginous,  excluding  the  types  already  mentioned,  several 
rows  are  present.  The  blood-vessel  system  of  Amphioxus 
differs  from  that  of  other  vertebrates  in  the  absence  of  a 
valvular  heart,  propulsion  of  the  blood-current  being  induced 
through  the  agency  of  a  number  of  contractile  chambers  de- 
veloped at  different  points  upon  the  arteries  and  veins.  There 
are  from  twenty-five  to  fifty  of  these  bulbs  on  either  side. 

Branchiae  are  arranged  in  all  fishes,  in  connection  with  the 
convex  surfaces  of  osseous  or  cartilaginous  arches  placed  on 
either  side  of  the  throat,  in  double  rows.  In  Amphioxus, 
these  rows,  from  seventy  to  eighty  in  number,  are  contained 
within  a  chamber  opening  anteriorly  by  the  mouth  and  pos- 


60  COMPARATIVE   ANATOMY. 

teriorly  by  the  alimentary  canal.  It  is  thus  at  once  a  bran- 
chial chamber  and  a  pharynx ;  hence  the  name  of  the  class, 
including  the  Amphioxus — Pharyngobranchiata.  The  pro- 
cess of  respiration  would  appear  to  be  aided  by  a  number  of 
very  vascular  processes  of  mucous  membrane  produced  from 
the  parietes  of  the  chamber  at  its  anterior  portion. — In  mar- 
sipobranchiates  the  branchiae  are  enclosed  within  pouches 
(hence  the  name  given  to  the  class)  upon  the  side  of  the 
body,  each  of  which  has  a  distinct  internal  and  external  ori- 
fice.*— In  Selachia  and  osseous  fishes,  the  arches  vary  from 
three  to  six  in  number;  the  branchial  interspaces  opening 
externally  by  a  number  of  distinct  apertures,  as  in  the  former, 
or  terminating  in  common,  and  protected  by  portions  of  skel- 
eton (operculum),  as  in  the  latter.  In  Selachia  each  branchia 
assumes  somewhat  a  ribbon-like  form  (hence  the  name  Elas- 
mobranchiata). — In  osseous  fishes  it  may  assume  the  form  of 
a  lobe  or  crest,  as  in  Hippocampus  (sea-horse),  or  that  of  a 
comb,  as  in  all  others. 

False  gills  are  vascular  appendages  to  gill  covers  of  certain 
Selachia. 

Swim  bladder.  This  is  a  simple  or  sacculated  hollow  viscus, 
present  in  many  fishes ;  absent  in  Scomber  (mackerel).  It  is 
oblong,  and  ordinarily  furnished  anteriorly  with  two  caeca. 
Possessed  of  a  smooth  fibrous  covering,  it  is  lined  with  a 
glistening  membrane,  exceedingly  rich  in  gelatine  (ichthyo- 
colla,  q.  v.),  and  at  one  portion  of  the  surface  is  remarkably 
vascular,  constituting  the  rete  mirabile.  The  swim  bladder,  as 
a  rule,  is  situated  directly  beneath  the  vertebral  column, 
rarely  within  a  vertical  fold  of  intestine,  and  thus  separated 
from  contact  with  the  abdominal  walls,  as  in  Campostoma. 

*  To  understand  the  relation  between  these  and  the  gills  of  ordinary 
fishes,  we  must  suppose  each  compressed  sac  to  be  split  through  its  plane, 
and  each  half  to  be  glued  by  its  outer  smooth  side  to  an  intermediate  sep- 
tum, which  would  then  support  the  opposite  halves  of  two  distinct  sacs ;  if 
then  these  vascular  surfaces  be  prolonged  in  gill-like  structure,  and  an  inter- 
mediate basis  of  support  be  given,  we  have  the  branchial  arch  of  a  Selachian, 
which  is  the  homologue,  not  of  a  single  gill  sac,  but  of  the  contiguous  halves 
of  two  distinct  gill  sacs.  (Carpenter.) 


CIRCULATORY   AND   RESPIRATORY   SYSTEMS.  61 

It  is  commonly  isolated,  yet  may  communicate  with  oesoph- 
agus, as  in  Lepidosteus  (gar),  or  be  obscurely  cellular  (pul- 
monic),  and  at  times  employed  in  respiration,  as  in  Lepido- 
siren  (mudfish).  Hence  the  swim  bladder  appears  in  some 
fishes  to  represent  a  rudimentary  lung. 

Relations  of  branchial  arches  to  stylo-hyoid  ligament  of  man. 
The  elements  in  the  hyoid  bone  of  osseous  fishes  are  as  fol- 
lows: basi-hyal,  ^glosso-hyal,  uro-hyal,  epi-hyal,  cerato-hyal, 
stylo-hyal;  brauchiostegal,  basi-branchial,  hypo-branchial, 
thyro-branchial,  cerato-branchial,  epi-branchial,  and  pha- 
ryngo-branchial  bones.  Operculum,  or  gill  cover  is  com- 
posed of  opercular,  pre-opercular,  inter-opercular,  and  sub- 
opercular  bones.  The  mechanism  of  respiration: — muscles 
producing  adduction  and  abduction  of  operculum. 

Batrachia. — Heart  composed  of  two  auricles  and  a  single 
ventricle.  The  venous  blood,  collected  by  the  ascending 
and  descending  cavse,  is  thrown  from  the  right  auricle  into 
the  single  ventricle,  thence  through  the  pulmonary  artery  to 
the  lungs,  to  be  returned  by  the  pulmonary  veins  to  the  ven- 
tricle to  be  sent  through  the  aorta  to  the  body.  Thus  the 
blood  of  a  batrachian  is  mixed  in  the  pulmonic  and  greater 
portion  of  the  systemic  circulation.  The  larval  form  of  some 
batrachians,  as  Eana  (frog),  breathe  by  gills,  and  in  certain 
forms,  as  Axolotl,  and  Proteus  (salamander),  these  are  retained 
throughout  life.  The  lung,  when  present,  is  a  double,  coarsely 
cellulated  sac.  The  mechanism  of  respiration: — muscles  of 
deglutition. 

Eeptilia. — Heart  generally  of  two  auricles  and  a  single 
ventricle.  A  rudimentary  septum  is  seen  partially  dividing 
the  ventricle  into  two  parts  in  Ophidia.  The  septum  is  per- 
fect in  the  Crocodilia,  making  four  cavities  to  the  heart. — 
The  general  plan  of  the  circulation  as  in  Batrachia,  excepting 
Crocodilia.  In  these  animals  the  venous  blood  contained  in 
the  right  ventricle  is  sent  not  only  to  the  lungs  through  the 
pulmonary  artery,  but  also,  through  a  second  large  trunk 
which  becomes  the  left  or  descending  aorta,  to  supply  the  ab- 
domen and  lower  extremities.  That  portion  of  the  blood  arte- 
rialized  and  returned  from  the  lungs  is  received  in  the  left 


62  COMPAEATIVE   ANATOMY. 

auricle,  thence  is  conveyed  to  the  left  ventricle,  to  be  sent  to 
the  head  and  upper  extremities  by  the  right  or  ascending 
aorta.  But  the  lower  portion  of  left  aorta  does  not  contain 
pure  venous  blood,  since  it  receives  blood  from  the  right 
aorta  through  -a  communicating  branch  (ductus  Botalli).  Nor 
does  the  right  aorta  at  all  times  contain  pure  arterial  blood, 
for  it  may  receive  venous  blood  from  the  right  ventricle 
through  an  opening  in  the  inter-aortic  septum. — Lung  is 
coarsely  cellulated ;  sometimes  single. — Mechanism  of  respi- 
ration in  Chelonia  by  the  muscles  of  flank  spaces  (inspira- 
tory)  and  muscles  within  breast  box  (expiratory) ;  in  Ophidia 
by  movement  of  xthe  ribs.  Red  blood  corpuscles  large,  gen- 
erally oval,  nucleated.  Portal  circulation  receives  blood  from 
kidneys,  posterior  extremities,  and  tail. 

Aves. — Heart  of  four  cavities.  Circulation  as  in  man,  ex- 
cepting that  the  aorta  turns  to  the  right.  Lungs  fixed,  double ; 
bronchi  communicate  with  cavities  of  bones  extensively  in 
Rhamphastos  (toucan);  slightly  in  Gallus  (fowl);  but  not  at 
all  in  Hirundo  (swallow). — Mechanism  of  respiration  resident 
in  abdominal  muscles — since  ribs  and  sternum  remain  fixed. 
Rudiment  of  a  diaphragm  in  Psittacus  (parrot).  Respiration 
of  egg  of  reptile  and  bird  through  allantois. 

Mammalia. — Heart  of  four  cavities ;  plan  of  circulation  as 
in  man.  In  Halicore  (dugong)  there  is  a  double  apex  to 
heart — one  for  each  ventricle.  Bone  exists  in  ventricular 
septum  in  ox.  Foramen  ovale  at  times  persistent,  as  in 
Phoca  (seal).  Several  methods  of  origin  of  the  great  arte- 
rial trunks  from  aorta.  With  the  ruminants  a  single  trunk 
from  the  arch  divides  into  the  subclavian  and  carotids ;  with 
the  carnivores,  the  innominate  artery  gives  both  carotids  as 
well  as  right  subclavian.  Anomalous  arrangements  of  these 
vessels  in  man  are  reproductions  of  the  normal  ones  of  the 
lower  mammals.  Curious  anastomoses  of  vessels  (wonder 
nets)  seen  in  Bradypus  (sloth)  and  Cetacea. 

The  general  plan  of  the  circulation  in  Yertebrata  can  be 
detected  in  the  development  of  the  blood-vessel  system  in 
man.  Thus  in  the  human  foetus,  the  five  cervical  arches  rep- 
resent the  five  branchial  arches  of  the  fish.  In  the  former, 


CIRCULATORY   AND   RESPIRATORY  -SYSTEMS.  63 

they  are  transient,  and  are  represented  in  the  infant  as  anas- 
tomoses between  the  arteries  of  the  neck.  But  in  the  latter, 
they  are  persistent,  and  sustain  the  branchiae  throughout  life. 
In  the  reptilian  heart,  the  transmission  of  venous  blood  from 
the  right  to  the  left  side  through  a  septal  foramen  recalls  the 
arrangement  seen  in  the  human  foetus  at  term. 

SPLEEN. 

The  spleen  is  an  appendage  to  the  blood-vessel  system. 
Commonly  oval,  it  is  seldom  narrow,  and  elongate,  as  in 
Perca  (perch).  Usually  single,  it  is  occasionally  double, 
as  in  Squatina,  or  multiple,  as  in  Lamna  (shark).  (Van  der 
Hoeven).  It  is  situated  in  the  cavity  of  the  abdomen  in  prox- 
imity with  the  stomach,  and  consists  of  a  red  parenchyma, 
supported  by  fibrous  bands  (trabeculae)  extending  inward 
from  a  capsule.  The  spleen  is  peculiar  in  the  arrangement  of 
its  blood-vessels.  The  splenic  artery  abruptly  terminates  in 
large  spaces  (lacunae),  from  the  opposite  sides  of  which  the 
splenic  veins  as  abruptly  begin.  Small  branches  of  the  ar- 
tery, prior  to  entrance  into  the  lacunae,  are  distributed  upon 
their  walls,  and  have  appended  to  their  smaller  twigs  a 
number  of  minute  white  bodies — the  splenic  corpuscles. 

Were  no  provision  made  for  the  reception  of  large  volumes 
of  blood  which,  from  various  causes,  are  poured  into  the 
vessels  of  the  abdominal  viscera  from  other  parts,  stagnation 
of  vascular  currents  supplying  organs  essential  to  nutrition 
might  at  any  time  occur.  It  is  thought  to  be  the  function  of 
the  spleen  to  avert  this  by  receiving  and  retaining  the  excess 
of  blood  until  an  equalization  of  currents  is  again  assured. 
This  view  would  seem  to  receive  confirmation  from  the 
organ  appearing  only  in  animals  having  a  complete  system 
of  vessels,  as  in  the  Yertebrata.*  With  others,  as  in  the 
Mollusca,  the  distensible  lacunae  (which  resemble  in  plan  of 
construction  that  of  the  splenic  lacunae)  are  placed  at  all  por- 

*  Other  animals  having  closed  vessels,  but  without  spleen,  as  Annelida, 
Amphioxus,  and  marsipobranchiate  fishes,  have  a  compensatory  feature  in 
the  extreme  dilatability  of  their  numerous  vascular  trunks. 


64  COMPARATIVE   ANATOMY. 

tions  of  the  body,  and  preclude  the  possibility  of  untoward 
pressure  upon  any  one  point. 

LYMPHATICS. 

The  lymphatics  are  accessory  to  the  sanguiferous  system. 
From  the  various  tissues  and  organs  they  collect  a  fluid 
(lymph)  which  is  apparently  a  transuded  portion  of  the  liquor 
sanguinis  unappropriated  by  the  tissues.  In  addition,  they 
derive  nutritive  material  through  the  villi  (lacteals)  from  the 
food  in  the  intestines.  The  liquids  thus  obtained  are  con- 
veyed from  smaller  to  larger  vessels,  until  finally  they  empty 
by  one  or  more  great  trunks  into  the  venous  circulation. 
(Leidy.) 

The  lymphatics  are  confined  to  Yertebrata,  and  are  con- 
stant among  its  tissues ;  exceptions;  spleen  of  Chelonia, — and 
ganglia  of  nervous  system.  They  are  abundant  without 
valves  or  glands,  as  in  Pisces;  abundant  with  valves,  but 
without  glands,  as  in  Reptilia;  less  abundant,  but  possessing 
both  valves  and  glands,  as  in  Aves  and  Mammalia. — Pulsatile 
vesicles  are  in  some  Yertebrata  associated  with  the  lymphat- 
ics, as  in  Anguilla  (eel),  and  Rana  (frog). 


IX. 

EXCEETOEY  SYSTEM, 

THE  function  of  removing  from  the  organism  the  results  of 
waste  of  tissue  is  called  excretion.  No  organ  is  specially 
devoted  to  it  among  the  Protozoa,  Radiata,  Mollusca  below 
Lamellibranchiata,  and  Articulata  below  Arachnida  and  In- 
secta.  Yarious  bodies,  apparently  glandular,  have  had  a 
depurative  office  attributed  to  them,  but  oftener  from  exclu- 
sion than  possession  of  any  certain  knowledge  of  their  nature. 
With  various  Articulata,  as  in  Insecta,  many  of  the  append- 
ages to  the  alimentary  canal  —  particularly  the  conglobate 
forms  emptying  their  products  near  the  oral  or  anal  extrem- 
ity— are  in  part  subservient  to  this  purpose.  The  labor  of 


EXCRETORY   SYSTEM.  65 

removing  excretory  elements  is  not  confined,  even  in  the 
highest  animals,  to  a  single  organ.  Thus  the  respiratory  ap- 
paratus may  receive  some  of  the  inorganic  elements,  such  as 
carbonic  acid  and  water;  other  excreta,  as  in  certain  air- 
breathing  animals,  may  exude  either  through  the  skin  (ex- 
halation), or  its  appendages,  viz.,  the  perspiratory  and  anal 
glands ;  whilst  others  may  find  their  way  into  the  intestines, 
to  be  voided  with  the  ejecta. 

Of  necessity  closely  associated  with  channels  of  nutrition, 
excretory  organs,  wherever  seen,  are  unusually  vascular.  It 
is  partly  from  the  recognition  of  this  feature  that  systems 
of  contractile  vessels,  having  corpusculated  contents,  like 
blood,  yet  opening  upon  the  exterior,  like  excretory  tubes, 
have  recently  been  assigned  a  position  midway  between  the 
circulatory  system  and  the  emunctories.  (See  p.  55.) 

Conspicuous  among  these  is  the  WATER-VASCULAR  SYSTEM. 
This  is  an  arrangement  of  vessels  seen  in  certain  aquatic  and 
entozoic  articulates,  which  contains  a  corpusculated  fluid 
communicating  with  the  external  medium  by  a  simple  open- 
ing. The  main  trunk  of  the  system  arises  from  this  point, 
and  divides  into  branches  which  are  distributed  through  the 
tissues.  The  walls  of  the  vessels  are  well  defined;  and  by 
their  pulsation,  a  to-and-fro  motion  is  given  to  the  contents, — 
permitting  water  to  enter  the  body  and  excrementitious  mat- 
ters freely  to  escape. 

The  water- vascular  system  is  best  developed  in  the  Ento- 
zoa,  q.  v. 

Rotifera. — The  external  aperture  is  situated  at  the  posterior 
end  of  the  body,  and  communicates  with  a  large  sac  which 
rhythmically  contracts.  From  this,  ciliated  trunks  arise, 
which  usually  give  off  short  lateral  branches,  to  terminate 
in  the  trochal  disk  of  the  animal. 

KIDNEY. 

The  kidney  is  that  organ  which,  being  specially  devoted  to 
excretion,  elaborates  a  crystalline  product.  This  is  constantly 
uric  acid  or  guanin,  either  free  or  combined.  With  many 

5 


66  COMPARATIVE   ANATOMY. 

highly  developed  animals  there  are  also  present  various  or- 
ganic bodies,  such  as  urea,  creatiu,  and  creatinin, — as  well  as 
inorganic  compounds,  as  phosphates  of  ammonia  and  mag- 
nesia.— Secretion  commonly  elaborated  from  venous  blood, 
but  in  Mammalia  partly  from  arterial  also. 

No  true  kidney  below  Mollusca. 

MOLLUSCA,  Organ  absent  in  Polyzoa,  Brachiopoda,*  and 
Tunicata. 

Lamellibranchiata. — The  kidneys  (organ  of  Bojanus)  al- 
ways double.  Each  is  an  oblong  gland  of  a  brown  or  brown- 
ish-yellow color,  placed  upon  dorsal  region  of  body,  near  the 
hinge  line,  beneath  pericardium  and  inferior  adductor  muscle. 
The  usually  very  thin  walls  of  these  two  sacs  have  numerous 
folds  or  plicse,  which  form  compartments  or  areolse,  all  of 
which  are  covered  with  ciliated  epithelium.  (Siebold.)  The 
short  excretory  duct  opens  into  mantle  upon  side  of  base  of 
foot,  and  is  generally  isolated  from  genital  pore,  or  is  in  cojn- 
mon  with  it.  Secretion  solid. 

Gasteropoda. — Organ  lamellose  without  cilia,  and  placed 
near  branchial  vein ;  in  Doris  at  region  of  membrane  about 
heart ;  in  pulmonic  types  at  posterior  and  upper  part  of  res- 
piratory chamber  between  the  heart  and  rectum.  It  is  pro- 
vided with  excretory  canal  opening  by  the  side  of  the  pneu- 
matic orifice,  as  in  Limax,  or  within  the  respiratory  chamber, 
as  in  Helix.  Secretion  solid. 

Cephalopoda. — The  kidneys  (spongy  bodies)  are  append- 
ages to  main  venous  canal.  The  renal  cells  are  placed  upon 
the  sides  of  everted  follicles,  the  bases  of  which  are  formed 
by  the  walls  of  the  vein  itself.  Each  cell  is  granulated,  and 
possesses  well-defined  nucleolar  elements^—  and  commonly  a 
crystalline  product.  The  urine  passes  along  an  imperfectly 
defined  duct  into  the  cavity  of  the  mantle,  thence  to  escape 
from  the  body  through  the  syphon. 

ARTICULATA.  Kidneys  absent  below  Myriapoda; — func- 
tion with  some  supplied  through  water-vascular  system. 

\ 

*  Hancock  looks  upon  the  'great  perivisceral  chamber  with  its  extensive 
ramifications'  of  Brachiopoda  as  having  a  renal  significance. 


EXCRETORY  SYSTEM.  67 

"When  present,  organ  follicular,  and  empties  in  intestine. 
Secretion  solid. 

Myriapoda. — Kidney  composed  of  long,  convoluted  tubes 
generally  opening  into  intestine  at  anterior  part. 

Arachnida. — Several  cseca  empty  into  intestinal  canal,  near 
its  termination,  a  solid  urine. 

Insecta. — See  p.  64. 

YERTEBRATA.  Kidneys  are  two  in  number,  and  generally 
situated  immediately  beneath  the  vertebral  columns.  Com- 
posed of  numerous  vascular  tufts  (Malpighian  bodies),  each  is 
placed  in  relation  with  the  termination  of  a  slender  tubule 
lined  with  mucous  membrane,  which  afterward  unites  with 
its  fellows  to  form  a  single  excretory  tube  (ureter).  The 
Malpighian  bodies  are  always  placed  toward  the  periphery  of 
the  organ :  when  the  layer  thus  occupied  is  well  defined,  it  is 
called  the  cortical  portion.  The  uriniferous  tubules  extend 
from  the  region  of  the  Malpighian  bodies  toward  the  centre : 
when  this  layer  is  well  defined,  it  is  called  the  medullary  por- 
tion.— The  urine  is  excreted  in  part  only  from  the  Malpighian 
tufts,  some  of  its  ingredients  being  elaborated  from  a  net- 
work of  small  veins  surrounding  the  uriniferous  tubules. 
This  network  results  either  from  division  of  the  return  blood 
of  the  renal  artery,  or  is  received  into  the  kidney  from  an- 
other source.  From  the  analogy  such  an  arrangement  bears 
to  the  portal  circulation  in  the  liver,  it  is  known  as  the  renal 
portal  circulation. 

Two  types  recognized.  (1)  Organ  not  separated  into  cort- 
ical and  medullary  portions;  tubules  may  be  ciliated,  and 
urine  solid ;  portal  vein  received  from  posterior  part  of  body 
and  lower  limbs,  when  present :  includes  Pisces,  Batrachia, 
Reptilia,  and  Aves.  (2)  Organ  separated  into  cortical  and 
medullary  portions ;  tubules  never  ciliated,  and  urine  always 
fluid;  portal  vein  received  from  renal  capillaries:  includes 
Mammalia. 

Pisces. — Kidneys  absent  in  Amphioxus.  With  others,  long 
and  narrow,  without  pelves,  and  placed  upon  either  side  of 
median  line,  immediately  beneath  bodies  of  vertebrae.  Ure- 
ters may  unite  and  form  one  tube  or  empty  separately  into 
rectum  from  above. 


68  COMPARATIVE   ANATOMY. 

Batrachia  arid  Reptilia. — Kidneys  compact,  deeply  situ- 
ated, often  firmly  connected  to  iliac  bones,  when  present,  by 
peritoneum,  as  in  Chelonia  and  Sauria.  Bladder  present 
with  many  Lacertilia  (lizards)  and  Batrachia.  Kidneys  of 
Ophidia  not  placed  on  same  level,  the  right  situated  more 
anteriorly  than  the  left;  the  structure  is  more  lobulated  and 
less  compact  than  in  Chelonia. 

Aves. — Kidneys  deeply  situated,  and  extend  from  lungs 
downward  as  far  as  rectum.  The  posterior  surface  is  moulded 
into  the  cavities  formed  by  the  bones  on  which  it  rests. 
There  is  no  pelvic  cavity,  and  the  ureters  empty  into  cloaca. 
(Johnson.) 

Mammalia. — Form  often  lobulated,  as  in  Rhinoceros,  and 
Phoccena  (dolphin).  The  urine  escapes  from  uriniferous  tu- 
bules into  pelvis,  to  empty  into  bladder  through  ureter, 
thence  to  be  voided  by  urethra. 


X. 

INTEGUMENT. 

THE  layer  of  tissue  investing  an  animal  is  called  the  integ- 
ument. In  the  embryonic  condition  of  many  of  the  lower 
forms  the  investment  is  continuous  over  the  surface  of  the 
body,  without  any  proper  processes  or  irregularities. 

PROTOZOA.     See  Skeleton  and  Spongia. 

RADIATA.  Coelenterata. — Integument  composed  of  a  sim- 
ple cellular  commonly  translucent,  thick  gelatinous  layer 
without  appendages.  In  Aurelia  (jelly-fish)  it  forms  a  loose- 
mass,  somewhat  resembling  connective  tissue,  interspersed 
with  occasional  elastic  filaments  and  muscular  fibre.  The 
hydroid  polyp  stalk  possesses  two  dermal  layers — one,  inner, 
is  cellular;  the  other,  outer,  is  structureless,  and  forms  a 
sclerous  covering  to  the  animal. 

Echinodermata. — Integument  more  or  less  calcified.  (See 
Skeleton.) 


INTEGUMENT.  69 

MOLLUSCA.  Polyzoa. — Integument,  represented  by  a  struc- 
tureless membrane,  containing  calcareous  or  siliceous  parti- 
cles, is  received  by  pullulation  into  skeleton,  q.  v. 

Brachiopoda. — Integument  contractile,  cleft,  forming  halves 
to  a  mantle*  placed  in  relation  to  shell,  q.  v.;  bud-like  pro- 
cesses, as  in  Polyzoa. 

Tunicata. — Within  the  integument  (test)  of  Ascidia  nu- 
merous cartilage-like  cells  are  in  relation  with  a  membranous 
matrix.  The  matrix  presents  great  diversities  of  structure, 
representing,  in  fact,  almost  every  known  tissue.  Thus  in 
one  genus  Ave  have  a  test  resembling  cartilage ;  in  another, 
bone ;  in  a  third,  connective  tissue.  In  Ascidia  the  integu- 
ment separates  into  two  layers,  but  in  Boltenia  the  tendency 
is  less  evident.  An  epithelium  results  from  the  imperfect 
metamorphosis  of  the  integumental  layer.  A  structureless, 
homogeneous  epidermis,  is  naked  and  wrinkled  in  Salpa, 
furnished  with  spines,  or  tesselated  in  some  species  of  Bol- 
tenia.  The  integument  of  Tunicata  possesses  the  remarkable 
property  of  elaborating  cellulose. 

Lamellibranchiata. — The  integument  generally  with  two 
openings,  as  in  Tunicata — one  for  the  admission  of  water, 
the  other  for  its  ejection.  These  often  take  the  form  of 
tubes  (siphons),  more  or  less  lengthened  and  projected  at 
will.  The  receiving  siphon  communicates  with  the  cavity 
included  between  the  branchiae,  the  discharging  one  with  an- 
other cavity  behind  the  leaves.  In  some  species,  however, 
the  discharging  siphon  is  alone  present.  In  Ostrea  (oyster) 
there  are  no  siphons,  the  mantle  being  entirely  open.  (Gosse.) 
— Edges  of  mantle  furnished  with  retractile  papillae,  rich  in 
glands  and  pigment  cells.  (For  shell,  see  p.  26.) 

Gasteropoda  and  Pteropoda. — Integument  a  dense  con- 
tractile derm  of  a  cellular  structure,  often  containing  pig- 
ment matter  free  or  in  cells.  It  is  covered  with  a  ciliated 
epithelium,  which  partially  or  entirely  covers  the  body.  Its 


*  '  Mantle'  will  be  restricted  to  that  fold  or  other  portion  of  the  integu- 
ment designed  to  elaborate  the  shell.  Where  both  shell  and  fold  are  absent, 
'test'  will  be  employed. 


70  COMPARATIVE   ANATOMY. 

surface  is  striated  or  tuberculated,  and  recalls  the  appearance 
of  a  mucous  membrane.  With  many  species  the  skin  forms 
around  the  neck  or  back  a  fold,  the  posterior  part  of  which 
(mantle)  is  dilated  into  a  hernial  sac  containing  a  portion  of 
the  viscera.  (Siebold.) — (For  shell,  see  p.  26.) 

Cephalopoda. — Integument  composed  of  a  contractile 
fibrous  tissue,  and  a  delicate  non-ciliated  lamellose  epi- 
dermis. Within  the  meshes  of  the  skin  a  number  of  con- 
tractile cells  (cromatophori)  are  lodged,  each  surrounded  by 
a  delicate  elastic  membrane.  The  pigment  granules,  which 
they  enclose,  are  always  of  the  same  color  in  each  cell,  and 
produce  the  blue  or  violet  or  yellowish-brown  spots,  whose 
extent  and  shade  vary  according  as  the  ceils  are  contracted  or 
dilated.  (Siebold.) 

ARTICULATA.  The  spines,  hairs,  and  scales  of  Crustacea, 
Arachnida,  and  Insecta  are  portions  of  the  true  skeleton,  q.v. 
Glandular  appendages  seen  in  Annelida. 

VERTEBRATA.  Integument  composed  of  two  well-defined 
layers — the  inner,  fibrous  (derm,  true  skin);  the  outer,  cellu- 
lar (epidermis,  cuticle). 

Pisces. — The  appendages  to  the  skin  form  the  exo-skele- 
ton.  This  is  composed  of  fins,  and  scales  or  plates;  arid  may 
be  calcareous,  osseous,  or  corneous.  Fins  are  vertical  folds 
of  integument,  either  entirely  dermal,  as  in  Anguilla  (eel),  or 
supported  by  bony  rays,  as  in  the  majority  of  osseous  fishes. 
Fins  are  named  from  their  locality — the  dorsal,  caudal,  anal, 
ventral,  and  pectoral  fins.  The  latter  is  not  a  true  fin,  but 
.in  part  a  representative  of  the  anterior  extremity  of  higher 
vertebrates.  The  caudal  fin  is  homocercal  when  rays  diverge 
both  above  and  below  the  position  of  vertebrae,  as  in  the  ma- 
jority of  recent  fishes ;  or  heterocercal  when  they  diverge 
from  the  under  surface  of  the  terminal  vertebrae,  as  in  Aci- 
penser  (sturgeon).  Scales  are  organs  analogous  to  horns  and 
nails  of  mammals.  They  may  be  inserted  into  skin  each  by 
a  species  of  socket  or  matrix,  which  is  formed  either  in  the 
true  skin  or  within  its  folds,  and  arranged  in  lamellae,  as  in 
majority  of  osseous  fishes,  without  order,  as  in  Anguilla  (eel), 
or  in  plates,  as  in  Acipenser  (sturgeon).  Those  with  a  rounded 


INTEGUMENT.  71 

free  edge  are  known  as  the  cycloid,  and  those  with  a  comb-like 
edge  the  ctenoid  scales.  When  the  scales  are  of  a  small  size 
and  irregular  form,  they  are  called  placoid,  but  when  large 
and  tesselated,  ganoid.  The  minute  anatomy  of  the  two  last 
varieties  may  more  or  less  closely  resemble  that  of  tooth  or 
bone.  All  fishes  have  an  abundant  mucoid  product  thrown 
off  from  the  cellular  sub-epidermic  la}rer.  It  is  especially 
abundant  about  the  gill  covers  and  along  the  '  lateral  line/ 
and  is  everywhere  exceedingly  copious  in  Anyuilla  (eel),  with 
which  the  scales  are  rudimentary. 

Batrachia. — Integument  loosely  attached  to  muscle,  and  is 
without  scales, — rarely  with  plates,  as  in  extinct  Labyrintho- 
don.  In  Eana  (frog)  the  whole  surface  of  the  epidermis  is 
beset  with  minute  trifid  apertures  leading  to  spherical  sacs. 
(Huxley.) 

Reptilia. — Integument  never  scaled ;  often  tuberculate, 
or  epidermis  assuming  form  of  tesselated  plates,  as  in  Chelo- 
nia.  In  Ophidia  and  Sauria  the  epidermic  plates  are  more 
or  less  laminated.  During  process  of  shedding  skin,  which 
occurs  periodically  with  Ophidia,  the  epithelial  layer  is 
thrown  off  entire.  No  glandular  appendages. 

Aves. — Integument  loosely  connected  to  muscle,  and  cov- 
ered with  feathers,  q.v.  Horny  beak,  spur,  and  tesselated 
plates  to  tarsi,  are  examples  of  cuticular  development. 
\Yhile  papillse  of  derm  may  be  pronounced,  glandular  ap- 
pendages are  absent. 

Mammalia. — Derm  well  developed;  papilla  generally 
small,  large  on  the  pads  of  feet,  or  on  muzzle.  Epidermis 
rarely  forming  a  connected  layer,  as  on  tail  of  Castor  (beaver), 
in  bone-like  plates,  as  in  Dasypus  (armadillo),  or  in  laminated 
processes,  as  in  Manis  (pangolin). 

Nails  are  flattened,  horny  plates  developed  from  the  upper 
surface  of  the  phalangeal  integument  only,  as  in  many  mon- 
keys and  man.  Claws  are  nails  which  embrace  a  larger 
portion  of  the  phalanx,  being  developed  not  merely  from  its 
upper  surface,  but  also  from  its  extremity,  and  extending  far 
round  on  its  sides,  as  in  carnivores.  In  the  dog  and  cat  a 
bony  plate  extends  from  last  phalanx  into  the  posterior  fold 


72  COMPARATIVE   ANATOMY. 

of  nail. — Hoofs  are  claws  with  the  terminal  portions  blunted 
and  rounded,  and  adapted  to  the  support  of  the  limb.  (Hux- 
ley.) Hollow  horns,  as  in  Ruminantia,  are  analogous  to 
claws,  but  solid  horns,  as  in  Rhinoceros,  are  without  bony 
support,  and  probably  are  the  result  of  coalescence  of  hairs. 
Two  kinds  of  glands,  sebaceous  and  sudoriferous.  The 
former,  almost  always  in  connection  with  hair  bulbs,  produce 
a  fatty  secretion.  The  latter  lie  within  the  subcutaneous  con- 
nective tissue  as  simple  tubes,  the  ducts  from  which  pursue 
a  more  or  less  wavy  course  to  open  on  the  skin.  In  most 
mammals  the  tube  is  coiled  at  its  commencement,  but  in  ox 
and  dog  it  is  straight.  In  the  latter  the  glands  upon  the  body 
are  rudimentary  caeca,  but  upon  the  ball  of  the*  foot  they  are 
large.  (Huxley.) 


XI. 

KEEVOUS  SYSTEM. 

NERVE  tissue  is  that  peculiar  product  of  organization  which, 
while  the  source  of  sensation,  controls  excito-motory  and  nu- 
tritive acts. 

Two  kinds  recognized,  cellular  and  commissural.* 
The  nerve  cell  is  globular  or  oval,  and,  possessed  of  at 
least  one  spherical  nucleus,  is  generally  unipolar  or  bipolar, 
rarely  multipolar.  A  collection  of  nerve  cells  constitutes  a 
ganglion.  A  commissure  may  be  either  a  prolongation  of  the 
cell  wall,  or  a  distinct  structure,  characterised  in  the  higher 
animals  as  a  white  thread-like  band,  having  an  axis  fibre,  en- 
closed by  a  medullary  sheath,  and  the  whole  supported  by 
basement  membrane  (neurilemma).  A  ' nerve'  is  a  bundle 
of  commissures.  Ganglia  are  supposed  to  generate  nerve 
power;  commissures  to  convey  it  from  ganglion  to  ganglion, 
or  to  and  fro  from  adjacent  structures.  The  nerves,  however, 

*  By  '  commissure '  is  assumed  a  band  which  not  only  unites  ganglion  with 
ganglion,  or  perceptive  area  with  ganglion,  but  also  associates  ganglion  with 
motor  area. 


NERVOUS   SYSTEM.  73 

are  not  entirely  passive  agents,  but  are  endowed  with,  a  pecu- 
liar property  (neurility). 

The  simplest  expression  of  a  nervous  system  is  a  ganglion 
placed  in  relation  with  a  pair  of  nerves.  One  of  these,  ex- 
tending from  the  tissues  (perceptive  areas)  to  the  ganglion,  is 
designed  to  convey  an  impression  to  the  centre  generating 
power,  and  hence  is  called  afferent,  or  sensory.  The  other, 
extending  from  the  ganglion  to  the  tissues  (excito-motor 
areas)  is  supposed  to  transmit  the  power  excited  to  activity 
by  the  reception  of  sensation,  and  hence  is  called  efferent, 
or  motor.  To  the  transfer  of  an  impression  either  way  the 
continuity  of  the  conductor  is  essential. 

The  complexity  of  a  nervous  system  is  determined  by  the 
number,  arrangement,  and  degrees  of  development  of  its 
ganglia  and  commissures. 

PROTOZOA.     No  nervous  system  apparent.* 

RADIATA.  Ccelenterata. — Form  of  nervous  system  not 
determined. 

Echinodermata. — The  plan  is  that  of  a  number  of  ganglia 
arranged  in  the  form  of  the  circle  or  pentagon,  connected  by 
commissures  and  sending  branches  to  the  surrounding  tissues. 
In  Asteracanthion  (star-fish)  the  ganglia  are  situated  at  points 
between  the  rays. 

MOLLUSCA.  A  number  of  ganglia  generally  surround  the 
gullet,  and  constitute  the  'cesophageal  ring.'  Other  ganglia 
are  seen  at  various  points  of  the  body  connected  with  the 
above,  and  with  one  another  by  commissural  threads,  their 
position  and  size  being  determined  by  the  relations  and  im- 
portance of  the  regions  concerned.  Processes  of  the  cell  wall 
often  extend  far  into  the  nerves,  while  the  distinct  neuri- 
lemma  contains  orange  or  reddish  pigment  cells. 

Polyzoa. — "No  nervous  „  system  has  with  certainty  been 
recognized. 

Brachiopoda. — An  oesophageal  ring,  composed  of  two  im- 


*  Animals  having  no  nervous  system  are  by  some  included  in  a  group 
named  the  Acrita. 


74  COMPARATIVE   ANATOMY. 

perfectly  defined  ganglia,  supplies  branches  to  mantle,  arms, 
and  viscera. 

Tunicata. — A  single,  often  yellowish  ganglion,  confined  to 
mantle,  is  placed  between  the  oral  and  atrial  openings. 

Lamellibranehiata. — The  ganglia  are  symmetrically  ar- 
ranged in  three  pairs.  The  members  of  the  first,  or  labial 
pair,  are  placed  one  on  either  side  of  the  gullet,  and  are 
united  by  a  slight  transverse  band  superiorly.  It  supplies 
the  parts  about  the  mouth  and  anterior  portions  of  the  vis- 
cera. The  second,  or  branchial  pair,  is  usually  placed  upon 
anterior  surface  of  posterior  adductor  muscle;  it  communi- 
cates by  long  nerves  with  the  labial  pair,  and  gives  branches 
to  the  adjacent  muscle,  branchiae,  and  mantle.  The  two 
ganglia  are  blended  when  the  branchiae  are  united  behind, 
as  in  Unio  (fresh-water  mussel).  The  third,  or  pedal,  is  con- 
fined to  the  foot.  "When  this  is  absent,  as  in  Ostrea  (oyster), 
the  ganglia  are  wanting;  but  when  it  is  largely  developed,  as 
in  Mytilus  (sea-mussel),  they  often  unite,  forming  a  single  bi- 
lobed  ganglion. 

Two  diffuse  cesophageal  rings  are  thus  formed, — one  occu- 
pying the  greater  part  of  the  visceral  mass  and  defined  in 
front  by  the  labial  and  branchial  ganglia,  the  other  by  the 
labial  and  pedal  ganglia,  and  both  on  the  sides  by  their  com- 
municating branches  respectively. 

Gasteropoda. — Ganglia  with  commissures  forming  cesoph- 
ageal  ring.  The  upper  part  may  be  recognized  as  the  brain, 
from  which  branches  are  distributed  to  the  eyes,  tentacles, 
and  adjacent  parts  of  mantle.  The  sub-oesophageal  ganglia 
always  connect  with  branchial  and  pedal  ganglia  by  conspic- 
uous commissures. — A  distinct  set  of  ganglia  intimately  asso- 
ciated with  the  mouth,  gullet,  and  stomach,  have  been  ob- 
served in  some  naked-gilled  forms,  as  Doris  and  Eolis.  It  is 
probably  analogous  to  a  sympathetic  system. 

Pteropoda. — The  nervous  system  resembles  that  of  Gas- 
teropoda, with  the  exception  that  the  supra-cesophageal  gan- 
glia are  absent. 

Cephalopoda. — The  ganglia  are  of  large  size,  and  are  more 
or  less  perfectly  enclosed  in  a  cartilaginous  brain  case.  (See  p. 


NERVOUS   SYSTEM.  75 

26.)  The  supra-  and  infra-oesophageal  ganglia  are  connected 
by  commissures,  as  in  Gasteropoda.  In  Nautilus,  the  latter 
are  two  in  number  and  placed  one  in  front  of  the  other.  The 
optic  nerve  arises  from  the  superior  ganglia;  the  olfactory 
nerve,  and  branches  for  the  tentacles  and  body,  arise  from  the 
inferior.  In  Argonauta,  the  ganglia  are  in  a  single  mass  in  the 
median  line,  the  optic  nerve  arising  from  the  lateral  portions. 
Brachial  nerves  enter  the  axis  of  the  tentacles,  and  are  fur- 
nished with  ganglia,  which  control  the  action  of  the  suckers. 

ARTICULATA.  The  ganglia  are  arranged  in  the  axial  line 
of  body  and  joined  by  a  double  chain  of  commissures,  ex- 
cepting Eotifera  and  Entozoa.  The  <  neural  cord,'  thus  con- 
stituted, lies  upon  the  ventral  aspect  of  the  segments.  Its 
anterior  portion  commonly  surrounds  the  oesophagus,  form- 
ing an  cesophageal  ring.  As  a  rule,  each  segment  retains  a 
pair  of  ganglia  with  its  afferent  and  efferent  nerves. 

Rotifera. — The  nervous  system  has  been  imperfectly  made 
out.  It  is  probably  not  strictly  conformable  to  that  of  the 
articulate  type. 

Entozoa. — See  p.  161. 

Annelida. — The  neural  cord  not  fixed  to  ventral  region, 
but  floats  freely  in  viscera.  Supra-cesophageal  ganglion  bir- 
lobed;  sub-cesophageal,  conspicuous.  Nemertes  differs  re- 
markably from  the  other  Annelida,  in  the  nervous  system 
being  without  apparent  enlargements,  and  composed  of  two 
separate  cords,  one  on  each  side  of  the  body,  which  send 
off  lateral  branches  along  their  course.  (Siebold.) 

Crustacea. — The  nervous  cord  is  usually  connected  to  ce- 
rebral ganglia  by  an  oesophageal  ring.  As  a  rule,  the  ganglia 
are  distinct;  but  in  certain  forms,  where  segments  of  the 
skeleton  are  fused  together,  those  portions  of  the  cord  cor- 
responding to  such  segments  form  one  mass,  within  which 
are  represented  the  elements  of  as  many  ganglia.  In  the 
higher  Crustacea,  as  in  Homarus  (lobster),  the  cord  forms 
two  separate  centres  of  ganglionic  union,  one  for  the  head 
and  thorax,  and  one  for  the  abdomen. 

Arachnida. — The  cord  forms,  as  a  rule,  two  enlargements, 
one  for  the  cephalo-thorax,  and  one  for  the  abdomen. 


76  COMPARATIVE   ANATOMY. 

Myriapoda  and  Insecta. — The  cord  presents  many  varieties 
of  form,  but  the  general  arrangement  is  similar  to  that  in 
other  articulates. 

The  nervous  system  of  an  insect  developing  by  true  meta- 
morphosis presents  a  distinct  form  for  each  condition,  as  fol- 
lows :  The  larval,  a  simple  duplex  gangliated  cord ;  the  pupal, 
in  addition,  a  degree  of  coalescence  of  the  ganglia ;  and  the 
imagal  or  sexual,  the  highest  degree  of  such  coalescence. 

VERTEBRATA.  Nervous  system  composed  of  a  cerebro- 
spinal  axis  with  branches,  and  a  sympathetic  system. 

The  cerebro-spinal  axis  is  placed  above  the  alimentary  tract, 
within  a  cartilaginous  or  osseous  chamber  (neural  canal),  and 
consists  of  numbers  of  ganglia  arranged  for  the  most  part  in 
pairs,  with  a  tendency  in  separating  to  form  median  cavities 
(ventricles).  It  is  divided  into  a  brain  (encephalon)  and  spinal 
cord  (medulla  spinals,  myelon).  In  the  spinal  cord  the  gray 
matter  is  arranged  in  ganglia  of  an  indefinite  number,  and 
placed  within  the  white  commissural  mass.  With  compara- 
tively few  exceptions,  it  fills  the  neural  canal,  and  contains 
throughout  its  whole  extent  a  narrow  ventricle,  which  ex- 
pands at  the  commencement  of  brain  into  the  fourth  ventri- 
cle.— Within  the  brain  the  gray  matter  is  placed  upon  the 
outer  side  of  the  commissural  mass.  The  ganglia  are  of  a 
fixed  number.  With  the  exception  of  Amphioxus,  this  num- 
ber is  four,  each  ganglion  receiving  a  distinct  name,  as  fol- 
lows: cerebellum,  optic  lobe,  cerebrum,  and  olfactory  lobe. 
Of  these  the  cerebellum  is  a  single  mass ;  the  others  are  in 
pairs,  excepting  olfactory  lobes  of  Rana  (frog),  cerebrum  of 
Squalus  (shark),  and  the  optic  lobes  of  Lepidosiren  (mudfish), 
which  present  no  tendency  to  divide.  Pituitary  and  pineal 
bodies  constantly  present ;  the  latter  are  "without  calcareous 
matter  below  man. 

Cranial  nerves  never  of  more  than  twelve  or  less  than  three 
pairs.  In  Amphioxus  these  are  (1)  trigeminal,  (2)  pneumogas- 
tric,  glossopharyngeal,  and  spinal  accessory  represented  in 
one,  and  (3)  hypoglossal.  The  olfactory  and  optic  nerves 
always  arise  from  their  respective  ganglia.  The  olfactory 
nerves  are,  properly  speaking,  those  branches  arising  from 


NERVOUS   SYSTEM.  77 

the  olfactory  bulbs  or  ganglia.  Their  roots  or  peduncles, 
originating  from  beneath  cerebrum,  are  of  the  nature  of  com- 
missures. Decussation  (chiasm)  of  the  majority  of  fibres  of 
optic  nerves  rarely  absent,  as  in  Amphioxus. 

The  medulla  oblongata  is  intermediate  in  character  to  the 
brain  and  spinal  cord.  It  is  composed  of  several  ganglia, — 
the  gray  matter  being  placed  internally.  With  it  all  the 
cranial  nerves  excepting  the  olfactory  and  optic  have  con- 
nection.* 

Sympathetic  system.  The  differences  obtaining  between  the 
representatives  of  this  system  are  not  sufficiently  defined  to 
require  comment. 

Pisces. — In  Amphioxus  the  spinal  cord  terminates  at  either 
end  without  enlargement.  The  position  of  the  brain  can 
only  be  recognized  by  the  points  of  origin  of  nerves  of  spe- 
cial sense.  The  spinal  cord  generally  is  thickest  at  the  middle 
third.  It  gives  off  fifty-five  to  sixty  pairs  of  nerves,  each 
nerve  arising  from  a  single  root. 

With  all  fishes,  except  Amphioxus,  the  brain  is  well  defined. 
— The  medulla  oblongata  is  slender,  not  distinctly  divisible 
into  pyramids.  It  is  often  open  from  above,  exposing  cavity 
of  fourth  ventricle,  and  possesses  on  either  side  a  number  of 
small  projections  known  as  the  lateral  lobes.  These  are  pecu- 
liar to  fishes,  and  in  Trigla  (gunard)  and  Torpedo  (electrical  tor- 
pedo) are  specially  marked.  —  Olivary  body  wanting. —  Cere- 
oellum  relatively  of  large  size,  generally  roundish  and  smooth, 
but  in  active  predatory  fishes,  as  Selackia,  hollow,  presenting 
transverse  folds,  and  commonly  communicates  with  cavity  of 
fourth  ventricle.  With  the  exception  of  Scomber  (mackerel), 
where  they  are  small,  it  is  entirely  devoid  of  lobes. — Optic 
lobes  are  of  large  size,  and  constitute  the  most  conspicuous 
and  bulky  mass  of  the  brain.  They  are  hollow,  occasionally 
communicate,  and  each  contains,  in  osseous  fishes,  a  rounded 
nodule.  The  optic  nerves  commonly  form  a  chiasm. — Cere- 
bral hemispheres  smaller  than  the  preceding,  solid,  separated 

*  It  will  be  included  in  description  under  head  of  'brain.' 


78  COMPARATIVE   ANATOMY. 

from  one  another  by  a  cavity  traversed  by  a  single  coramis- 
sural  band.  Immediately  in  advance,  the  olfactory  lobes 
arise ;  they  are  particularly  large  in  Selachia.  Pituitary 
body  well  developed;  infundibulum  generally  long,  as  in 
Gadus  (haddock). — Pineal  body  a  small  globe  of  gray  matter 
situated  between  optic  lobes,  very  distinct  in  Anguilla  (eel) ; 
less  apparent  in  other  species.  In  Salmo  (salmon)  it  consti- 
tutes a  plexus  of  slender  vessels,  anastomosing  to  form  a 
club-shaped  mass.  In  Squalus  (shark)  it  is  particularly  dis- 
tinct, being  larger  than  in  any  other  fish  (Wyrnan). — The 
brain,  as  a  whole,  is  small,  and  forms  but  about  j^-g-  part  of 
the  axis.  It  does  not  fill  the  brain  case, — a  quantity  of  loose 
adipose  tissue  being  placed  around  it. 

Batrachia. — Spinal  cord  extends  the  length  of  the  verte- 
brae excepting  in  some  tailless  forms,  as  Rana  (frog).  Brain 
resembles  in  general  features  that  of  Pisces.  The  region  of 
cerebellum  less  developed;  the  cerebellum  is  a  small  flat- 
tened transverse  band  continuous  on  either  side  with  medulla 
oblongata,  which  is  without  lateral  lobes. — Optic  lobes  large, 
conspicuous. — Cerebrum  larger  than  in  Pisces,  and  extends 
with  but  slight  or  no  constriction  into  large  olfactory  lobes. 
Optic  thalami  and  corpora  striata  present.  Each  portion  of 
the  brain  hollow,  and  lined  with  ciliated  epithelium,  except- 
ing optic  thalarni  and  cerebellum,  which  are  solid. 

Reptilia. — Spinal  cord  contains  a  canal  which  in  Sauria 
and  Ophidia  extends  as  far  as  the  first  coccygeal  vertebrae. 
In  Chelonia  it  is  shorter.  Brain. — The  cerebellum  consists 
of  a  median  portion  only.  The  fourth  ventricle  is  open  from 
above,  but  is  closed  in  Chelonia.  Optic  lobes  of  a  rounded 
form,  and  contain  a  ventricle  which  communicates  with  the 
third  ventricle. 

The  posterior  portion  of  each  lobe  is  constricted  trans- 
versely in  Python.  Cerebral  hemispheres  more  developed 
than  in  fishes,  larger  than  optic  lobes,  smooth,  hollow,  and 
imperfectly  subdivided  into  lobes.  Each  hemisphere  enfolds 
a  portion  of  pia  mater  and  contains  upon  the  base  of  its 
ventricle  representatives  of  the  corpora  striata  and  optic 
thalami.  The  third  ventricle  is  traversed  by  the  anterior 


NERVOUS   SYSTEM.  79 

and  posterior  commissures,  the  middle  being  absent.  Olfac- 
tory lobes  large,  hollow,  possessing  chambers  which  com- 
municate with  the  ventricles  of  the  cerebral  hemispheres. 
The  brain  relatively  larger  than  that  of  the  fish.  In  the  frog 
it  forms  ^-^  part  of  the  whole  tract.  But  in  the  tortoise  is 
much  less,  viz.,  gg1^  part.  It  does  not  fill  brain  case,  and,  as 
in  fishes,  is  on  the  same  plane  with  spinal  cord. 

Aves. — Spinal  cord  smaller  in  mass  than  brain.  It  com- 
pletely fills  spinal  canal.  A  narrow  ventricle  runs  through 
its  middle.  Conspicuous  swellings  are  noticed  at  the  points 
of  origin  of  brachial  and  sacral  plexuses.  At  the  latter 
position  a  distinct  ventricle  (sinus  rhomboidalis)  is  seen, 
lined  with  ependyma  and  containing  a  fold  of  pia  mater. 

Medulla  oblongata  without  pyramids  or  olivary  bodies. 
Cerebellum  joining  with  cerebral  hemispheres  to  conceal  the 
ganglia  beneath.  It  is  without  lateral  lobes  and  folded. 
Transverse  section  displays  the  arbor  vitse. — Optic  lobes  hol- 
low, united  into  a  single  rounded  mass  of  small  size  and 
concealed  by  junction  of  the  cerebellum  and  cerebral  hemi- 
spheres.—  Cerebral  hemispheres  relatively  longer  than  in 
reptiles  and  fishes ;  heart-shaped  with  the  apex  directed  for- 
ward ;  lobes  not  convoluted.  Corpus  callosum  present  as  a 
rudiment ;  fornix  small  or  wanting.  Bodies,  so  called,  cor- 
pora striata  and  optic  thalami  present;  former  not  striated; 
latter  not  united  by  commissure,  and  joining  with  optic  lobes 
in  origin  of  optic  nerves. — Olfactory  lobes  large,  apparently 
appendages  to  anterior  lobes  of  cerebral  hemispheres.  Olfac- 
tory nerve  escapes  from  cranium  through  a  single  opening. 

The  brain  is  relatively  larger  than  that  of  either  fishes 
or  reptiles,  is  placed  at  an  obtuse  angle  to  spinal  cord,  and 
entirely  fills  brain  case.  In  Fringilla  canaria  (canary)  it  com- 
prises 2-  of  whole  tract,  in  Anas  (duck)  3^. 

Mammalia. — Spinal  cord,  with  but  few  exceptions,  fur- 
nished with  ventricle.  It  is  swollen  at  points  of  origin  of 
brachial  and  sacral  plexuses,  and  frequently  shorter  than  its 
enclosing  canal, — the  intervening  space  being  occupied  by 
the  obliquely-placed  nerves  (cauda  equina). 

Medulla  oblongata  }s  divided  into  pyramids  and  lateral 


80  COMPARATIVE   ANATOMY. 

tracts;  a  conspicuous  ganglion  (olivary  body)  is  added. — The 
body  (vermiform  process)  of  the  cerebellum  is  small  and 
transversely  folded.  Its  lateral  appendages  (hemispheres) 
have  now  a  size  exceeding  that  of  the  body.  They  are 
united  inferiorly  by  a  band  of  commissures  (Pons  Varolii) 
which  traverse  the  course  of  fibres  going  to  form  the  crura 
cerebri,  and,  with  but  few  exceptions,  by  another  smaller  set 
(trapezium),  which  cross  immediately  in  advance  of  the  ante- 
rior pyramids. — The  optic  lobes  (corpora  quadrigemina)  are 
small,  concealed  from  above,  and  are  bi-partite,  or  imper- 
fectly quadri-partite. — The  cerebral  hemispheres,  exceeding 
in  size  other  portions  of  the  brain,  are  divided  into  lobes, 
most  generally  convoluted,  and,  with  few  exceptions  (Impla- 
centalia),  united  by  commissure  (corpus  callosum). — Corpora 
striata  striated. — Optic  thalami  at  times  give  partial  origins 
to  optic  nerves. — Olfactory  lobes  rudimentary  in  man,  but 
large  and  containing  ventricle  in  Ovis  (sheep). — As  a  rule, 
the  relative  size  of  the  brain  is  greater  than  in  that  of  any 
other  class  of  Yertebrata,  occupying  in  ox  ^9  in  Elephas 
(elephant)  5^,  in  Vulpes  (fox)  -tb,  an(i  in  man  40  Part  of  the 
whole  tract. 

Monotremata. — Spinal  cord  in  Ornithorhynchus  (duck  bill) 
is  long,  slender,  and  fills  the  canal.  In  Echidna  (porcupine 
ant-eater)  it  is  thicker  and  shorter,  and  extends  but  half 
the  length  of  the  canal. — Medulla  oblongata  with  pyramids 
and  olivary  bodies  defined. — Cerebellum  large,  folded;  me- 
dian portion  with  small  lobes.  —  Optic  lobes  quadri-partite 
(Echidna);  median  fissure  faint,  sometimes  absent.  —  Cere- 
brum, with  great  commissure  absent.  Hemispheres  smooth 
in  Ornithorhynchus;  slightly  convoluted  in  Echidna,  where 
three  equidistant,  transverse  folds  characterize  the  posterior 
portion  of  each  hemisphere.— Olfactory  lobes  relatively  very 
large.  In  Ornithorhynchus  a  portion  of  the  nerve  arises  from 
the  inferior  surface  of  the  posterior  part  of  the  cerebrum 
behind  the  quadrigeminal  body.  In  Echidna  the  nerve  is  yet 
larger;  it  arises  from  the  anterior  part  of  the  cerebral  hemi- 
spheres, and  contains  a  prolongation  of  the  lateral  ventricle. 
Cerebral  hemispheres  encroach  very  slightly  upon  cerebellum. 


NERVOUS    SYSTEM.  81 

Marsupialia.  —  Olfactory  lobes  large,  for  the  most  part 
rounded  and  constricted.  Cerebrum  not  encroaching  upon 
cerebellum,  is  irregularly  lobed  and  smooth.  In  Macropus 
(kangaroo)  and  some  other  forms,  small  lateral  appendages 
lie  in  fossa  upon  petrous  portion  of  temporal  bone.  Corpus 
callosum  rudimentary,  and  in  some  genera  entirely  absent. 
Optic  lobes  quadri-partite.  Relative  size  of  brain  less  than 
in  other  Mammalia.  In  Dasyurus  (dasyure),  it  is  1  to  520,  in 
Phascolomys  (wombat),  1  to  614,  and  in  Macropus^  1  to  800. 

Hodentia. — Brain  —  Cerebrum  generally  of  a  rounded 
shape,  not  impinging  upon  cerebellum,  and  without  convo- 
lutions. Optic  lobes  quadripartite;  nates  larger  than  testes. 
Cerebellum  of  moderate  proportions,  with  well-marked 
hemispheres. 

Cetacea. — Brain  large,  that  of  the  Balcena  (whalebone 
whale)  weighing  three  pounds  four  ounces.  Cerebrum, 
nearly  covers  in  the  cerebellum,  is  broader  than  long;  the 
convolutions  are  numerous  and  deep.  Olfactory  lobes  rudi- 
mental,  and  were  believed  to  be  absent.  The  hemispheres 
of  cerebellum  divided  into  a  number  of  lobes,  six  on  either 
side,  obtained  for  the  most  part  by  subdivision  of  the  lobules 
mentioned  in  human  anatomy.  Trapezium  absent. 

Quadrumana.  —  The  brains  of  all  the  old  world  monkeys 
below  the  Anthropoids  possess  the  following  characteristics 
when  compared  to  that  of  man.  The  breadth  of  encephalic 
mass  is  proportionately  greater  than  the  length;  the  cere- 
bral hemispheres  do  not  cover  the  whole  of  the  cerebellum ; 
the  convolutions  are  smaller  and  less  deep;  the  sensory  gan- 
glia are  of  small  size;  the  corpora  albicantia  are  united  into 
one  mass;  the  cerebellum  is  smaller  and  Pons  Yarolii  conse- 
quently less.* 

*  The  above  resume  gives,  it  is  thought,  the  principal  variations  seen  in 
the  nervous  system  of  Mammalia. 


82  COMPARATIVE   ANATOMY. 

XII. 

ANIMAL  ELECTRICITY  AND  PHOSPHORESCENCE, 

ANIMAL   ELECTRICITY. 

THE  following  are  electrical  animals : 

Fishes.  —  Torpedo  oculata;  Raia  batis;  Raia  clavata;  Gym- 
notus  electricus;  Malapterurus  electricus;  Tetraodon  electricus; 
Trichiurus  electricus. 

Articulates. — Scolopendra  electrica. 

Torpedo  oculata.  The  disk  is  somewhat  broader  than  long,  abruptly 
rounded  in  front ;  the  tail  is  as  long  as  the  disk.  The  distance  from  the 
beginning  of  the  ventral  fin  to  its  free  end  is,  as  a  rule,  considerably  smaller 
than  the  distance  from  that  to  the  end  of  the  ventral  fin.  In  the  young 
individual  the  border  of  the  spiracle  is  surrounded  with  five  to  nine  teeth; 
these  are  lost  in  the  more  aged.  The  dorsal  fins  have  rounded  angles,  and 
convex  or  straight  posterior  borders.  The  caudal  fin  is  either  longer  than 
high  or  the  length  and  height  are  equal. 

The  coloration  is  subject  to  variation.  The  prevailing  tint  of  the  dorsal 
region  may  be  reddish  brown  with  bluish  spots  around  the  eyes,  varying  in 
number  between  seven  and  one.  If  a  few  of  these  alone  be  present  they 
are  situated  in  the  median  line  of  back.  Or  the  spots  may  be  of  a  white 
color,  scattered  over  the  region  of  back.  These  have  a  palish  border,  with 
an  intense  central  spot  of  a  copper  color.  Or  the  points  surrounding  the 
spiracles  may  be  absent,  and  in  place  of  the  bluish  spots  a  uniform  brown 
color  be  prevalent,  with  a  few  whitish  spots  scattered  over  the  surface. 

Measurements. — From  the  tip  of  nose  to  mouth,  1"  1"';  from  the  mouth 
to  anus,  5"  9'";  from  anus  to  end  of  caudal  fin,  5"  6'";  length  of  disk,  6" 
3'";  breadth  of  disk,  7".  Habitat.— The  Mediterranean  Sea  and  Atlantic 
Ocean.  (Muller  and  Henle.) 

Anatomy  of  Electrical  Organs.— The  electrical  organs  occupy  a  large 
part  of  the  broad  expansions  of  the  body,  which  in  the  other  allied  fishes 
are  formed  only  by  the  lateral  fins.  They  form  two  separate  masses,  one  on 
either  side  of  the  head  and  gills.  Each  is  an  irregular  ellipsoid,  convex  on 
either  side,  its  long  diameter  not  quite  parallel  to  the  axis  of  the  body,  and 
extending  outward  to  the  cartilaginous  margins  of  the  great  fins,  and  poste- 
riorly to  the  cartilage  which  separates  the  thoracic  from  the  abdominal  cavity. 
Their  form  and  the  honeycomb  embossments  of  their  surfaces  can  be  distin- 
guished through  the  skin  both  of  the  dorsal  and  ventral  aspects.  The  com- 
mon integuments  being  removed,  two  strong  fascial  coverings  are  discovered 


ANIMAL   ELECTRICITY   AND    PHOSPHORESCENCE.  83 

investing  the  electrical  organs.  The  outer  one  has  longitudinal  fibres,  which 
are  rather  loosely  adherent,  and  around  the  margin  of  the  organs  seem  to 
inosculate  with  the  skin.  The  inner  fascia  is  of  considerable  density,  forms 
the  immediate  tunic  of  the  electric  columns,  and  sends  delicate  processes, 
with  an  accompanying  network  of  arteries,  veins,  and  nerves,  down  between 
them  to  form  their  partitions.  Throughout  their  whole  extent  the  essential' 
part  of  the  electrical  organs  is  formed  by  a  whitish  soft  pulp,  divided  into 
numerous  pentagonal  prisms  by  the  fascial  processes  above  mentioned. 
These  lie  closely  together,  parallel  with  one  another,  and  perpendicularly 
between  the  dorsal  and  ventral  surfaces  of  the  fish,  so  that  their  extremities 
are  separated  from  these  surfaces  only  by  their  fascia  and  the  common  in- 
teguments. When  these  are  removed,  the  columns  present  something  of  the 
appearance  of  a  honeycomb.  The  columns  are  longest  next  to  the  head  and 
gills,  and,  being  at  these  points  about  one  inch  in  length,  thence  gradually 
diminish  outwardly,  until  on  the  external  margin  they  are  only  about  one- 
sixth  of  the  length  of  the  internal  ones.  Most  of  these  columns  are  either 
irregular  pentagons  or  irregular  hexagons;  a  few  are  nearly  tetragonal. 
They  are  united  to  one  another  by  short  but  strong  fibres,  and  by  a  reticular 
expansion  of  tendinous  threads  spread  over  them.  Their  number  varies 
considerably  according  to  the  age  of  the  fish,  but  averages  about  470  to 
each  organ.  (Coldstream.) 

The  nerves  distributed  to  the  electrical  organs  are  of  great  size.  They 
consist  of  three  principal  trunks  arising  from  the  cerebro-spinal  system. 
The  two  anterior  are  portions  of  the  fifth  pair ;  the  third  is  a  branch  of  the 
tenth.  They  appear  to  arise  in  part  from  an  appendage  to  the  cerebellum 
('fourth  encephalic  lobe'),  and  terminate  upon  the  sides  of  the  columns  by 
loops. 

Rudimentary  conditions  of  an  electrical  apparatus  are  met  with  in  other 
rays,  as  for  example  Raia  batis  (skate)  and  Raia  clavata.  Each  of  these 
possess  an  electrical  organ  imbedded  in  the  muscles  of  the  tail.  It  com- 
mences on  either  side  of  the  caudal  region,  at  about  one-third  of  its  length 
from  the  base,  and,  extending  toward  the  tip,  gradually  occupies  much  of  its 
space.  Its  form  is  that  of  a  tube  surrounded  by  a  nervous  covering.  It  is 
supplied  by  spinal  nerves,  which  resemble  in  their  distribution  those  of  other 
electrical  organs.  (Murray.)  The  electricity  elicited  from  this  apparatus  is 
similar  to  though  weaker  than  that  from  the  Torpedo.  (Robin.) 

Gymnotus  electricus  (electrical  eel). — Body  long,  eel-like,  naked,  without 
dorsal  fin,  covered  with  mucoid  secretion.  Head  is  short,  somewhat  flat- 
tened from  above  downward,  and  furnished  with  a  number  of  mucous  folli- 
cles. Mouth  large,  lips  thick  and  mobile.  Upper  jaw  a  little  longer  than 
lower,  and  furnished  with  a  number  of  small  acute  teeth.  The  tongue  is 
large  and  furnished,  together  with  the  pharynx,  with  a  number  of  small 
papillae.  The  eyes,  which  are  situated  upon  the  superior  aspect  of  head,  are 
very  small,  and  each  possess  a  yellowish  iris. 


84  COMPARATIVE   ANATOMY. 

The  general  hue  of  the  animal  is  blackish,  relieved  by  a  number  of  lighter 
spots,  some  of  them  having  a  reddish  tinge.  Lateral  line  double,  one  pass- 
ing near  the  median  line  of  back, — in  other  in  line  with  the  anal  fin.  Pec- 
toral fins  small,  anal  fin  long,  caudal  fin  obtuse.  (Blooch.) 

Anatomy.  The  abdominal  cavity  is  short ;  anus  placed  a  short  distance 
behind  branchial  cleft.  The  electrical  organs  occupy  nearly  one-third  of  its 
whole  bulk.  They  are  formed  by  two  series  of  tendinous  membranes,  one 
of  which  consists  of  horizontal  plates  running  from  the  abdominal  cavity 
towards  the  tail,  placed  one  above  another,  with  short  distances  between 
them  ;  the  other  of  perpendicular  plates,  forming,  along  with  the  other  series, 
small  quadrangular  cells,  which  are  filled  with  a  semi-gelatinous  transparent 
substance.  This  structure  is  divided  longitudinally  into  two  pairs  of  distinct 
organs,  one  considerably  larger  than  the  other.  The  greater  pair  lies  above 
the  other,  and  immediately  beneath  the  long  muscle  of  the  tail.  They  are 
separated  from  one  another  by  part  of  these  muscles,  by  the  air  bladder, 
and  by  a  central  membranous  partition.  They  occupy  a  large  portion  of  the 
lower  and  lateral  parts  of  the  body,  and  are  covered  externally  only  by  the 
common  integuments.  The  smaller  pair  are  covered  also  by  the  muscles  of 
the  caudal  fin.  Both  pairs  of  organs  are  somewhat  angular  in  their  trans- 
verse section,  truncated  anteriorly,  tapering  towards  the  tail.  In  a  Gymno- 
tus  of  average  length  the  larger  organ  of  one  side  is  about  one  inch  and 
one-quarter  in  breadth  at  its  thickest  part,  and  in  this  space  there  are  thirty- 
four  longitudinal  septa.  The  smaller  organ  is  about  half  an  inch  in  breadth, 
and  contains  fourteen  septa,  which  are  slightly  waved.  These  septa  prob- 
ably answer  the  same  purpose  as  the  columns  in  Torpedo. 

The  nerves  of  the  electrical  organs  are  derived  from  the  spinal  marrow 
alone.  They  are  large,  numerous,  and  divided  into  fine  twigs  on  the  cells  of 
the  organs  (Coldstream.) 

Measurements. — 5'  to  5'  3"  long. 

Habitat. — Amazon  River,  S.  A. 

Malapterurus  electricus  (raasch,  thunder-fish). — This  fish  belongs  to  the 
Siluridae  (cat-fishes). 

Malapterurus. — Only  one  dorsal  fin,  which  is  adipose,  and  situated  be- 
fore the  caudal ;  anal  of  moderate  length,  or  short ;  caudal  rounded ;  ventrals 
six-rayed,  inserted  somewhat  behind  the  middle  of  the  body ;  pectorals  with- 
out pungent  spine.  Barbels  six ;  one  to  each  maxillary,  and  two  on  each 
side  of  the  mandible.  Both  jaws  with  bands  of  villiform  teeth  ;  palate  eden- 
tulous. The  entire  head  and  body  covered  with  soft  skin.  Eyes  small.  Gill 
opening  very  narrow,  reduced  to  a  slit  before  the  pectoral.  An  electric 
organ  extends  over  the  whole  body,  and  is  situated  between  two  aponeu- 
rotic  membranes  below  the  external  integument. 

M.  electricus. — Description.  Rays  to  anal  fin  10-13.  Eye  rather  small, 
the  diameter  being  less  than  one-third  its  distance  from  the  upper  end  of  the 
gill  opening.  The  length  of  the  head  is  contained  four  times  and  a  third  in 


ANIMAL   ELECTRICITY   AND    PHOSPHORESCENCE.  85 

the  total  (without  caudal).  Jaws  equal  in  front.  The  outer  mandibulary 
barbels  extend  to  the  root  of  the  pectoral  Body  with  more  or  less  numerous 
small  roundish  black  spots,  a  part  of  which  are  sometimes  confluent  into 
larger  irregular  patches  ;  anal  and  caudal  fins  with  a  white  margin.  Dorsal 
vertebra  17  ;  caudal  22. 

Habitat. — Nile,  and  rivers  of  the  west  coast  of  Africa. 

The  only  organ  that  can  be  regarded  as  connected  with  the  electrical 
function  in  this  fish  is  a  thick  layer  of  dense  connective  tissue  which  com- 
pletely surrounds  the  body  immediately  beneath  the  integument.  So  com- 
pact is  it  that,  at  first  sight,  it  might  be  mistaken  for  a  deposit  of  fatty 
matter;  but,  under  the  microscope,  it  appears  to  be  composed  of  tendinous 
fibres,  closely  interwoven,  the  meshes  of  which  are  filled  with  a  gelatinous 
substance.  This  organ  is  divided  by  a  strong  aponeurotic  membrane  into 
two  circular  layers,  one  outer,  lying  immediately  beneath  the  derm,  the  other 
internal,  placed  above  the  muscles.  Both  organs  are  isolated  from  the  sur- 
rounding parts  by  a  dense  fascia,  excepting  where  the  nerves  and  blood- 
vessels enter.  The  cells  or  meshes  in  the  outer  organ,  formed  by  its  reticu- 
lated fibres,  are  rhombic  in  shape,  and  very  minute,  so  as  to  require  a  lens 
to  see  them  well.  The  component  tissue  of  the  inner  organ  is  somewhat 
flaky,  and  also  cellular. 

The  nerves  of  the  outer  organ  are  branches  of  the  fifth  pair,  which  runs 
beneath  the  lateral  line  and  above  the  aponeurotic  covering  of  the  organ. 
This  aponeurosis  is  pierced  by  many  holes  for  the  transmission  of  the  nerves, 
which  are  lost  within  the  cellular  tissue  of  the  organ.  The  intercostals 
supply  the  inner  organ  ;  their  electrical  branches  are  numerous  and  remark- 
ably fine.  (Ooldstream.) 

M.  Beninsis,  M.  Affinis. — Species  closely  resembling  above.  Habitat. — 
Old  Calabar.  (Gunther.) 

Of  the  electrical  power  of  Tetraodon  electricus  and  Trichiu- 
rus  elecfacus,  as  well  as  Scolopendra  electrica,  little  is  known. 

Animal  electricity  presenting  so  many  features  in  common 
with  that  derived  from  inorganic  sources,  was  at  one  time 
believed  to  be  identical  with  it.  The  idea  originated  with 
Galvani,  who  discovered  that  by  bringing  a  current  in- 
duced by  placing  two  metallic  plates — one  of  copper  and 
the  other  of  zinc — in  contact  with  the  nerve  of  a  leg  of  a 
dead  frog,  contraction  of  its  muscles  ensued.  (Galvanism.) 
He  inferred  from  this  that  he  had  re-supplied  the  force  re- 
moved by  death,  and  that  the  nervous  power  and  the  agent 
he  had  employed  were  convertible.  His  opinion  received 
apparent  confirmation  from  the  fact  that  all  electrical  organs 


86  COMPARATIVE   ANATOMY. 

are  largely  supplied  with  nerves,  as  well  as  from  the  obser- 
vation that  portions  of  the  brain  (gray  matter  of  cerebral 
hemispheres)  and  the  terminal  branches  of  certain  nerves  of 
sensation  (Paciriian  corpuscles,  Wagnerian  corpuscles,  con- 
junctival  corpuscles)  resembled  in  construction  electrical  ma- 
chines. But  it  was  afterward  found  that  nerve  power  could 
not  take  the  place  of  an  electrical  current.  A  string  tied 
round  a  nerve  produces  paralysis  of  motion  beyond  the  ob- 
structed point;  but  no  ligature  upon  a  metallic  conductor 
can  obstruct  an  electrical  current.  If  the  nerves  going  to  a 
muscle  be  cut,  the  muscle  is  rendered  incapable  of  contract- 
ing. If  the  nerves  going  to  an  electric  organ  be  severed, 
the  organ  can  no  longer  give  out  electric  discharges.  But  if 
the  dead  organ  be  taken,  electricity  can  be  developed  from 
it  in  the  same  manner  as  it  can  in  an  organic  voltaic  pile. 
Animal  electricity  is  essentially  a  life  product. 

ANIMAL   PHOSPHORESCENCE. 

Animal  phosphorescence  is  confined  to  the  Invertebrata. 

The  majority  of  phosphorescent  animals  are  marine.  Con- 
spicuous among  these  forms  is  the  Noctiluca  miliaris.  This  is 
a  small  sub-rounded  animal,  about  one-sixtieth  of  an  inch 
in  diameter,  composed  of  a  structureless  and  somewhat  dense 
integument,  and  furnished  with  a  long  sub-cylindrical  filiform 
tentacle.  Mouth  simple,  situated  upon  under  surface  of  body 
and  behind  tentacle ;  from  its  base  a  very  delicate  filament 
protrudes,  which  exhibits  a  rapid  undulatory  motion.  In  ad- 
vance of  mouth,  and  between  it  and  tentacle,  a  horny-looking 
bifid  ridge  is  present, — the  so-called  tooth.  (Huxley.)  Intes- 
tine and  anus  not  determined.  The  i nucleus'  a  strongly  re- 
fracting oral  body  of  about  4$-$  inch  in  length.  By  some 
considered  a  radiate,  Noctiluca  is  more  properly  classified 
with  the  Protozoa. 

Among  other  animals  possessing  this  property  are  many 
coelenterate  radiates,  and  some  echinoderms;  Salpa  and  Pyros- 
oma  among  molluscs;  and  various  Infusoria,  Annelida,  and 
Crustacea.  Among  light-bearing  terrestrial  forms  may  be 


SPECIAL   ORGANS.  87 

mentioned  the  Pyrophorus  luminosus  (cucujo),  a  large  beetle 
of  Cuba ;  Lampyris  noctiluca  (English  glow-worm) ;  Photinus 
stintillans  (small  firefly,  lightning  bug) ;  Photuris  pennsylvanica 
(large  firefly) ;  and  Scolopendra  electrica  (electrical  centipede). 


XIII. 

SPECIAL  OBGAtfS, 

A  SPECIAL  ORGAN  is  one  subservient  to  a  function  ordina- 
rily not  essential  to  the  economy  of  the  individual.  It  may 
be  of  a  peculiar  structure,  or  consist  of  modifications  of  a 
kind  already  existing.  Of  the  first  an  example  is  found  in 
ink-gland  of  Sepia  (cuttlefish);  of  the  second,  in  venom- 
gland  of  Caudisona  (rattlesnake). 

A  special  organ  may  have  a  sexual  significance  (see  p.  102), 
but  more  commonly  is  intended  for  purposes  of  offense  and 
defense. 

When  a  special  organ  is  designed  exclusively  for  reception 
of  external  impressions,  it  is  called  a  SENSE  CAPSULE.  In  its 
simplest  expression  a  sense  capsule  is  a  chamber  having  con- 
nection on  one  side  with  a  nervous  filament.  It  follows  that 
among  the  lowest  animals  no  sense  capsules  are  found.  But 
at  the  earliest  point  where  differentiation  of  function  occurs 
and  organ-making  begins,  they  not  infrequently  attain  to  pro- 
portions and  degrees  of  development  far  in  advance  of  other 
apparatuses. — Such  special  organs  stand  in  exacter  relation 
to  habit,  and  particularly  to  the  medium  in  which  the  animal 
lives,  than  to  its  zoological  position.  Thus  in  the  higher  Ce- 
phalopoda the  shelled  Nautilus  has  an  eye  of  much  simpler  con- 
struction than  its  naked  congener,  the  Sepia.  In  Talpa  (mole), 
living  under  ground,  the  eye  is  rudimentary  or  absent;  but 
its  near  associates,  living  above  ground,  have  it  fully  devel- 
oped.— There  is  a  power,  however,  apart  from  influence  of 
surroundings,  which  controls  the  production  of  sense  capsules, 


88  COMPAEATIVE   ANATOMY. 

namely :  the  capacity  for  general  development  possessed  by 
animals  of  a  given  type.  In  Radiata  where  this  is  small, 
the  eye  or  ear  are  never  seen  to  attain  that  degree  of  com- 
plexity secured  by  Articulata  or  Mollusca. 

LASSO    CELLS. 

Affixed  to  tentacles  of  Physalia  (Portuguese  man-of-war), 
Cyanea,  Emoryne,  Hydra,  Astrangia,  Actinia,  etc.  are  peculiar 
cell-like  structures,  endowed  with  the  property  of  exciting, 
on  contact  with  a  sentient  surface,  a  prickling  or  stinging 
sensation. 

The  essential  feature  to  a  stinging  apparatus  is  a  filiferous 
capsule.  This,  within  an  oval  or  ovoidal  cell,  contains  a 
spirally  wound  thread,  or  consists  of  smaller  cells,  each  con- 
taining, in  addition,  a  style  extending  from  one  pole  to  about 
the  centre  of  the  cell.* 

ORGANS   OF   TOUCH. 

PROTOZOA.  Parts  specially  designed  for  exercising  the 
sense  of  touch  do  not  exist,  if  the  long  lash-like  appendages 
(flagella)  to  certain  Infusoria  be  not  excepted. 

RADIATA.  Excluding  the  lasso  cells,  no  organs  of  touch 
are  met  w7ith  in  Ccelenterata.  The  tentacles  are  in  part  sub- 
servient to  this  purpose. 

*  Under  circumstances  not  readily  explained,  the  cells  eject  their  contained 
threads  with  an  astonishing  degree  of  rapidity;  in  so  doing  the  cells  are  ab- 
solutely turned  inside  out,  and  remain  attached  to  the  emptied  cells  as  long 
extended  tubes.  From  the  smaller  cells  the  style  is  also  extruded,  and  then 
appears  as  a  more  expanded  portion  of  the  thread,  with  which  it  is  contin- 
uous at  one  end  and  the  capsule  at  the  other.  An  attentive  examination  of 
the  extruded  thread  exhibits  a  more  complicated  structure  than  would  have 
been  suspected,  and  its  exact  character  is  extremely  difficult  to  ascertain. 
In  the  case  of  the  larger  capsules  a  spiral  arrangement  is  readily  distin- 
guishable, extending  the  entire  length  of  the  extruded  thread.  This  arrange- 
ment, in  some  instances,  appeared  to  depend  upon  minute  cilia  which  project 
at  right  angles  from  the  thread  and  apparently  pursue  a  spiral  course  ;  but 
in  other  instances  it  appears  as  if  the  thread,  during  its  eversion  of  the 
capsule,  assumed  a  spiral  course  within  the  portion  preceding  it,  and  that 
the  thread  externally  was  encircled  at  regular  intervals  with  non-vibrating 
cilia.  (Leidy.) 


SPECIAL   ORGANS.  89 

Echinodermata. — In  oral  tentacles,  ambulacra  and  pedicel- 
larise,  the  sense  of  touch  partially  resides. 

MOLLUSCA.  The  tentacles  of  Polyzoa  and  Brachiopoda, 
the  papillae  on  free  edge  of  mantle  of  Lamellibranchiata,  the 
conspicuous  cephalic  tentacles  of  Gasteropoda,  Pteropoda, 
and  Cephalopoda  are  doubtless  of  tactile  significance. 

ARTICULATA.  Organs  of  touch  resident  toward  cephalic  ex- 
tremity. In  Annelida  processes  of  various  forms  and  degrees 
of  complexity  are  observed.  They  are  generally  inarticu- 
lated,  though  sometimes  have  distinct  segments.  In  Crus- 
tacea, Myriapoda,  and  Insecta,  in  addition  to  palpi  to  certain 
parts  of  mouth,  jointed  processes  to  cephalic  segments 
(antennae)  are  present.  (See  p.  41.)  In  Arachnida  antennae 
are  absent.  Palpi  rarely  absent, — forficulate  in  certain  scor- 
pions, as  Thelyphomis  and  Phrynus.  Anterior  feet  in  latter 
resemble  antennae  both  in  construction  and  use. 

VERTEBRATA.  Pisces. — The  tumid  lips  of  many  fishes  and 
adjacent  barbels  are  organs  of  touch.  Special  organs  are  in 
addition  met  with  in  the  integument.  Placed  within  a  canal 
running  beneath  the  'lateral  line'  of  osseous  fishes,  and  ex- 
tending thence  to  opercular  and  maxillary  regions,  are  num- 
bers of  special  sense  organs.  These  consist  of  cellular  struct- 
ures appended  to  knob-like  terminal  filaments  of  the  fifth  or 
tenth  pair  of  nerves.* 

The  Pacinian  corpuscles  are  thought  to  be  analogous  to 
these  tactile  organs. 

Batrachia  and  Reptilia. — Special  organs  of  touch  absent. 
Tongue  generally  protrusile  and  tactile. 

Aves. — Sense  of  touch  located  in  tongue  and  parts  about 
the  bill. 

*  Each  knob  is  covered  by  a  coat  consisting  of  tiers  of  much  elongated 
cylindrical  cells.  Its  substance  consists  of  more  or  less  gelatinous  connect- 
ive tissue.  In  the  osseous  fishes  this  nerve  usually  perforates  the  peculiarly 
modified  scale  of  the  lateral  line,  which  supports  and  encloses  the  canal  at 
these  points.  In  the  cartilaginous  fishes,  the  canals  have  sometimes  special 
fibro-cartilaginous  coats;  or,  if  sacculi,  a  number  of  them  may  be  contained 
in  a  common  cartilaginous  investment,  as  in  the  Chimera.  Leydig  insists, 
with  great  justice,  on  the  identity  of  the  structure  of  these  organs  with  that 
of  the  semicircular  canals  of  the  ear.  (Huxley.) 


90  COMPARATIVE   ANATOMY. 

Feathers  are  appendages  to  dermal  papillse.  The  feather- 
sac  or  follicle  is  an  involution  of  the  integument,  having 
at  its  base  a  modified  tactile  papilla.  The  derm  constitutes 
the  fibrous  wall  of  the  follicle,  the  elements  of  the  epidermis 
comprising  the  root  sheaths.  These  sheaths  are  two  in 
number,  an  outer  and  inner.  The  former  is  placed  in  con- 
tact with  the  fibrous  wall  of  follicle,  the  latter  (first  '  striated' 
membrane)  with  the  developing  feather.  A  second  'striated' 
membrane  lines  the  shaft  of  the  quill. — The  bulb  is  a  collec- 
tion of  cells  surrounding  the  papilla,  from  which  are  devel- 
oped the  constituent  parts  of  the  feather. 

Every  feather  is  composed  of  an  outer  cortical  and  an 
inner  medullary  portion.  It  is  divided  into  regions,  as  fol- 
lows: vane  (shaft,  'quill'),  primary  branches  (barbs),  which 
give  off  secondary  branches  (barbules) — these  in  turn  origin- 
ating tertiary  branches  (barbulinse).  In  the  majority  of 
feathers  the  proximal  part  of  the  vane  has  its  barbs  and  bar- 
bules long,  loose,  and  floating,  so  as  to  form  a  compact  downy 
mantle  next  the  skin  of  the  bird,  to  retain  the  high  tempera- 
ture of  the  body.  In  the  rest  of  the  vane  the  barbs  are  more 
firm,  straight,  regular,  and  united,  to  assist  in  flight,  or  to 
protect  the  body.  (Grant.) 

Mammalia. — Organs  of  touch  highly  developed.  The  tac- 
tile (Wagnerian)  corpuscles  upon  terminal  branches  of  nerves 
to  the  hand  of  man  furnish  marked  examples. 

Hairs  are  appendages  to  dermal  papillae.  The  hair  sac  or 
follicle  closely  resembles  the  feather  follicle,  but  lacks  the 
lining  membrane  to  shaft;  the  latter  possesses  an  addi- 
tional covering — the  cuticle.  The  cuticle  on  that  portion 
of  the  hair  which  lies  within  the  sac  is  composed  of  two 
layers.  In  man  the  outer  layer  ceases  at  the  level  of  the 
sebaceous  glands;  and  the  edge  of  the  plates  of  the  inner 
layer  lie  very  closely  appressed  to  the  shaft.  In  many  of  the 
lower  animals,  however,  as  in  some  bats,  the  plates  are  at  a 
greater  angle  to  the  axis  of  the  hair,  and  their  projecting 
edges  give  rise  to  the  most  elegant  sculpturing  of  its  surface. 
(Huxley.)  Although,  wherever  developed,  hairs  are  consid- 
ered as  organs  of  special  sense,  it  is  particularly  about  the 


SPECIAL   ORGANS.  91 

snout  that  they  are  employed   in  exercising  the  sense  of 
touch,  as  in  whiskers  (vibrissse)  of  many  quadrupeds. 

ORGANS   OF   SMELLING. 

Many  Invertebrata  possess  the  sense  of  smell ;  but  with 
them  no  organs  have  been  definitely  assigned  the  function.* 

YERTEBRATA.  Pisces. — The  nasal  capsules,  two  in  num- 
ber, are  placed  one  upon  either  side,  on  periphery  of  body, 
commonly  at  a  point  midway  between  the  eye  and  snout. 
Each  consists  of  a  depressed  rounded  chamber,  lined  with  a 
very  vascular  plicated  membrane,  and  in  some  cartilaginous 
forms  covered  with  ciliated  epithelium.  Nose  rarely  com- 
municates with  palate,  f 

Batrachia  and  Reptilia. — Nasal  apparatus,  in  common  with 
all  Yertebrata  above  fishes,  is  contained  within  a  diverticu- 
lum  from  respiratory  canal.  In  Proteus  the  peripheral  por- 
tion is  plicated,  as  in  fishes,  but  opens  upon  palate,  behind 
upper  lip.  Region  of  turbinated  bone  cartilaginous.  With 
others,  olfactory  nerves  are  distributed  upon  the  mucous 
membrane  lining  the  anterior  portion  of  the  '  girdle  bone ;' 
and  are  separated  from  one  another  by  a  median  partition. 
In  Crocodilia  the  anterior  nares  may  be  closed  by  muscular 
action.  In  Ophidia,  turbinated  bones  rudimentary;  nasal 
glands  present. 

Aves. — Anterior  and  posterior  nares  well  defined;  latter 
often  unite  to  form  a  single  opening,  covered  with  protecting 
papillae.  The  turbinated  bones  are  larger  than  in  reptiles, 
though  the  convoluted  portion  of  the  ethmoid  is  yet  but  par- 
tially ossified.  Conspicuous  nasal  glands  constantly  present. 

*  To  the  antennae  of  insects  have  been  assigned  the  double  function  of 
smell  and  hearing.  There  can  be  very  little  doubt  that  the  former  sense  is 
so  situated,  and,  by  the  diversity  of  form  of  the  small  fossits  seen,  it  is  pos- 
sible that  those  of  a  larger  size  and  greater  depth  pertain  to  hearing.  (Horn.) 

f  There  is  great  reason  to  believe  that,  suited  to  their  surrounding  ele- 
ment, the  nasal  capsules  of  fishes  are  much  more  sensible  of  odorous  bodies 
dissolved  in  water,  and  applied  by  its  medium,  than  we  should  be  if  the 
application  of  the  object  was  to  be  made  to  our  organ  of  smell  by  the  same 
medium.  (Monro.) 


92  COMPARATIVE   ANATOMY. 

Mammalia. — Nasal  cavities  complicated  by  sinuses  occu- 
pying superior  maxilla,  sphenoid  and  frontal  bones;  eth- 
moidal  scrolls  greatly  developed.  Turbinated  bone  long  and 
comparatively  simple  in  Ruminantia,  but  elaborately  convo- 
luted in  many  Carnivora.  Exterior  openings  of  nostrils 
valvular  in  diving  animals,  as  in  Castor  (beaver).  The  space 
including  the  nostrils,  when  not  prolonged  beyond  the  lips, 
is  called  the  muzzle;  when  moderately  extended,  the  snout, 
as  in  Sus  (hog);  when  conspicuously  developed,  the  proboscis, 
as  in  Elephas  (elephant). 

EYE. 

The  eye  is  the  organ  of  vision.  To  adapt  itself  to  the 
function  of  receiving  upon  a  nervous  expansion  a  series  of 
external  images  or  diffused  rays  of  light,  the  anterior  portion 
of  the  capsule  is  transparent,  convex,  and  very  generally 
placed  upon  the  periphery  of  the  body.  The  wall  of  the  cap- 
sule is  the  sclerotica;  its  anterior  arc,  the  cornea;  the  liquid 
contents,  the  humors;  the  nervous  expansion,  the  retina ;  and 
the  nerve  filament,  the  optic  nerve.  These  characters  are  es- 
sential to  an  eye.  Accessories  both  within  and  without  the 
organ  add  to  its  complexity.  Eyes  may  be  single,  agglom- 
erate, or  compound. 

In  the  lowest  animals  the  essential  features  of  eye  and  ear 
resemble  one  another  so  intimately  that  it  is  with  difficulty 
that  the  organs  are  distinguished.  As  a  rule,  the  constantly 
vibratile  action  sustained  by  the  otolithes  may  serve  to  iden- 
tify an  ear,  since  the  analogous  body  in  the  eye  (crystalline 
lens)  is  more  fixed. 

PROTOZOA.     Eyes  wanting. 

RADIATA.  Many  radiate  animals  possess  capsules  upon  the 
edges  of  the  body,  as  in  Aurelia  (jelly-lish),  or  near  tentacles, 
as  in  Syncoryne.  Immediately  behind  the  corneal  portion, 
and  within  the  chamber,  are  occasionally  lodged  movable 
polygonal  crystals  of  carbonate  of  lime  (crystalline  lens), 
which  are  generally  of  a  red  color. 

MOLLUSCA.     Polyzoa  and  Brachiopoda. — Eyes  wanting. 


SPECIAL    ORGANS.  93 

Tunicata. — With  Ascidians  eight  pigment-  or  eye-specks 
(ocelli)  have  been  detected  at  the  entrance  of  the  respiratory 
tube;  and  six  of  a  deep  yellow  color  at  the  entrance  of  the 
anal  tube.  (Owen.) 

Lamellibranchiata. — Eyes  often  numerous.  Each  possesses 
a  highly  refractive  crystalline  lens,  and  a  pigment  lining 
(choroid  coat)  forming  an  iris  anteriorly.  They  may  be  sit- 
uated along  the  margin  of  mantle,  or,  as  in  burrowing  forms, 
around  the  orifices  of  the  breathing  tubes. 

Gasteropoda. — Eyes,  when  present,  two  in  number,  situ- 
ated at  the  extremities  of  tentacles  in  fresh- water  and  pulmo- 
nate  forms, — at  the  outer  side  of  base  in  marine.  In  the 
latter  case  they  are  fixed,  but  in  the  former  can  be  protruded 
and  protracted  at  will.  A  conspicuous  optic  nerve  traverses 
each  tentacle.  The  crystalline  lens  often  lenticular,  and  vit- 
reous humor  viscid.  Eye  particularly  conspicuous  in  Strombus, 
Natica,  and  Bulla.  Janihina  is  without  eyes.  In  Strombus  a 
sclerotic  coat,  choroid,  iris,  crystalline  lens,  and  cornea  are 
present. 

Cephalopoda. — The  Tetrabranchiata,  as  in  Nautilus,  have 
small  sub-hemispherical  eyes  placed  upon  pedicles,  and  are 
probably  without  crystalline  lens.  —  In  Dibranchiata,  as  in 
Sepia,  the  eye  is  singularly  complex.  Within  an  orbit  formed 
in  great  part  by  the  integument,  the  bottom  of  the  cavity 
alone  being  cartilaginous,  is  placed  the  eyeball  covered  ante- 
riorly by  the  skin.  This  is  very  thin  and  transparent  where 
it  extends  in  front  of  the  eye,  to  assume  the  function  of  a 
cornea.  The  sclerotic  coat  is  incomplete  in  front,  and  per- 
forate behind  through  numerous  openings  for  the  passage  of 
branches  of  the  optic  nerve.  The  second  tunic,  the  retina, 
is  thick,  and  extends  forward  in  a  remarkable  manner  to  the 
anterior  portion  of  the  eye  where  it  appears  to  hold  the  crys- 
talline lens  in  position.  The  pigment  layer  (choroid  coat)  is 
apparently  placed  within  the  retinal  layer.  In  this  anomalous 
position  it  is  din^c^tlxTunderstand  how  rays  of  light  can  pass 
through  the  pigment  layer  to  be  received  upon  the  optic  ex- 
pansion. With  some  cuttlefishes  a  granular  nerve-like  layer 
has  been  recognized  within  the  pigmental  layer  which  has 


94  COMPARATIVE    ANATOMY. 

received  the  name  of  the  'pre-pigmental  retina/  though  no 
connection  between  it  and  the  optic  nerve  has  been  demon- 
strated. The  crystalline  lens  is  unique  in  being  divided  trans- 
versely into  two  parts — an  anterior  and  a  posterior — between 
which  a  fold  of  choroid  membrane  is  inserted.  The  posterior 
segment  is  much  larger  than  the  anterior,  and  projects  back- 
ward into  the  interior  of  the  eye. — At  the  posterior  part  of 
the  orbit  a  closed  cavity  is  limited  in  front  by  the  eyeball,  and 
behind  by  a  layer  of  the  sclerotica,  which,  extending  back- 
ward, encloses  the  terminal  portion  of  the  optic  nerve  and  a 
gangliform  enlargement  upon  its  trunk. — Between  the  globe 
of  the  eye  and  cornea  is  seen  a  chamber  resembling  a  serous 
cavity,  but  which  communicates  with  the  external  medium 
by  a  minute  central  opening.  Its  lining  membrane  is  analo- 
gous to  that  of  a  conjunct! val  surface. 

ARTICULATA.  Annelida. — Simple  eyes  not  unfrequent  in 
the  dorsibranchiates.  For  eyes  of  Hirudo  (leech),  see  p.  159. 
Remarkably  large  form  in  Torrea. 

Crustacea. — Eyes  agglomerate  and  extremely  brilliant  in 
Daphne.  To  a  mass  of  ocelli,  often  chiefly  composed  of  pyri- 
form  lenses,  a  single  cornea  is  found.  Compound  aggregated 
eye,  either  sessile  or  pedunculated,  seen  in  Decapoda,  as 
Homarus  (lobster).  Fine  illustrations  of  compound  eye  met 
with  in  extinct  trilobites. 

Cirripedia  (barnacles)  — Eyes  multiple;  remarkable  for 
being  concealed  within  abdomen — rays  of  light  transmitted 
through  the  tissues. 

Insecta. — Eyes  single  or  compound,  aggregated.  When 
compound,  each  ocellus  possesses  a  flattened  cornea,  a  pris- 
matic vitreous  humor,  and  between  the  two  a  layer  of  vari- 
ously-colored pigment  matter.  One  optic  nerve  supplies  all 
the  ocelli  of  a  mass,  each  ocellus  being  furnished  with  a  dis- 
tinct branch  from  the  main  trunk;  the  so-called  'retina'  is 
an  expansion  of  nerve-like  substance  between  the  secondary 
and  terminal  subdivisions  of  the  nerve. 

The  ocelli  in  the  majority  of  insects  are  arranged  in  two 
lateral  masses,  one  on  either  side  of  the  head,  each  mass 
being  made  up  of  large  numbers  of  eyes.  In  Musca  (house- 


SPECIAL   ORGANS.  95 

fly),  they  are  400  in  number;  in  LibeUuta,  12,000;  in  Mwdella, 

25,088. 

VERTEBRATA.  Pisces. — Eye  compressed  antero-posteriorly; 
sclerotica  thick,  sometimes  bony,  as  in  Cephaloptera  (devil- 
fish); crystalline  lens  globular;  iris  fixed:  pupil  in  Anableps  ^c 
(star-gazer),  double.  Surrounding  the  entrance  of  the  optic 
nerve  into  the  eye  of  osseous  fishes  is  seen  a  crescentic  body,  | 
called  the  'choroid  gland.'  It  is  not  glandular,  but  erectile, 
being  composed  of  congeries  of  blood-vessels.  Its  use  is  not 
certainly  known.  It  may  assist  in  accommodation,  by  push- 
ing the  retina  forward  during  turgescence. — The  eye  of  the 
fish  is  adapted  to  focusing  through  a  dense  medium  under 
great  pressure. 

Reptilia. — General  features  of  eye  those  of  other  air-breath- 
ing vertebrates.  Certain  extinct  animals,  as  Ichthyosaurus -, 
had  a  more  complex  sclerotica  than  any  extant  forms.  It  was 
composed  of  a  number  of  distinct  plates,  by  which  the  focus- 
ing distance  could  be  regulated  by  muscular  action.  (See 
Aves.)  Rudiments  of  this  structure  can  be  detected  in  the 
eyes  of  certain  Chelonia  and  Sauria. — The  Chameleon  can 
i|move  eyes  in  opposite  directions.  Pupil,  as  a  rule,  fixed, 
slit-like. 

Aves. — Most  peculiar  feature  witnessed  in  rapacious  bird, 
where  the  sclerotic  coat  is  composed  of  a  number  of  plates 
arranged  in  the  long  diameter  of  the  organ,  capable,  by 
mutual  compression,  of  elongating,  or,  by  relaxation,  of 
shortening  the  axis  of  the  organ.  By  this  means  an  object 
of  prey  can  be  distinguished  at  a  great  distance  while  it  is 
equally  visible  at  the  moment  it  is  seized.  Within  the  choroid 
tunic  a  peculiar  body,  called  from  its  appearance  the  pecten, 
is  situated :  it  is  a  fold  of  the  choroid,  and  is  often  attached 
to  the  capsule  of  the  lens.  Its  function  is  unknown. 

Mammalia. — Eye  closely  resembles  that  of  man.  Is  slightly 
compressed  antero-posteriorly  (as  in  fishes)  in  certain  aquatic 
animals,  as  in  Phoca  (seal).  Eye  rudimentary  in  Talpa  (mole). 

Appendages  to  eye. — Conjunctiva  well  defined,  excepting  in 
fishes,  where  it  is  rudimental  and  yields  no  secretion. 

In  Reptilia  lachrymal  gland  makes  its  appearance  for  the 


96  COMPARATIVE  ANATOMY. 

first  time;  eyelids  without  cilia.  Third  eyelid  (nictitating 
membrane)  present  both  in  reptiles  and  birds.  This  struct- 
ure is  a  transparent  elastic  membrane,  which  while  at  rest 
lies  folded  up  at  inner  side  of  eyeball.  It  is  moved  across 
the  front  of  the  eye  by  appropriate  muscles  situated  at  the 
back  of  the  organ.  These  muscles  are  two  in  number,  and 
are  named  from  their  shapes  the  quadrate  and  pyramidal 
muscles.  "The  first  of  these  arises  from  the  sclerotica  at 
the  upper  and  back  part  of  the  globe  of  the  eye,  and  its 
fibres  slightly  converge  as  they  descend  toward  the  optic 
nerve,  above  which  they  terminate  in  a  semilunar  tendinous 
sheath  having  no  expressed  or  fixed  insertion.  The  pyra- 
midal muscle  arises  from  the  sclerotica,  from  the  lower  and 
nasal  side  of  the  eyeball;  its  fibres  converge  as  they  pass 
to  the  upper  side  of  the  optic  nerve,  and  there  terminate  in 
a  small  round  tendon,  which  glides  through  the  pulley  at 
the  free  margin  of  the  quadratus,  and  winding  round  the 
optic  nerve,  passes  along  a  cellular  sheath  at  the  lower  part 
of  the  sclerotica,  and  is  inserted  into  the  lower  part  of  the 
margin  of  the  third  eyelid,  along  which  it  is  continued  for 
some  distance,  and  is  gradually  lost."  (Owen.) 

In  birds  an  additional  gland  (gland  of  Harder)  is  placed 
upon  inner  surface  of  orbit,  and  furnishes  a  secretion  resem- 
bling that  from  the  Meibomian  follicles  of  mammals. — 
Mammals  possess  both  lachrymal  glands  and  Meibomian 
follicles. — Quadrupeds  have  two  orbital  muscles  in  addition 
to  those  seen  in  man, — a  retractor  and  compressor. 

EAR. 

The  ear  is  the  organ  of  hearing.  The  auditory  capsule 
(labyrinth)  receives  sonorous  vibrations  upon  its  anterior  sur- 
face, and  conveys  them  across  the  fluid  contents  to  act  upon 
the  nervous  expansion  (acoustic  nerve).  The  impression  is 
intensified  through  the  agency  of  one  or  more  free  motile 
sclerous  particles  (otolithes,  otoconites,  lapilli,  ear-stones,  ear- 
dust)  almost  constantly  present.* 

*  These  are  wanting  in  Amphioxus  and  marsipobranchiate  fishes.  (Mliller.) 


SPECIAL   ORGANS.  97 

With  the  Invertebrata  the  peculiarities  noticed  in  different 
animals  are  due  to  the  position  of  the  sac,  as  well  as  to  the 
number  and  color  of  its  otolithes.  The  motility  of  the  latter 
is  thought  to  be  due  to  presence  of  cilia  within  the  capsule. 
The  organ  is  wanting  below  Radiata. 

RADIATA.  In  Medusa  the  ears  are  numerous,  and  are  placed 
at  regular  intervals  along  the  margin  of  the  disk,  each  con- 
taining one  or  more  refractile  otolithes.  In  Geryonia  the  cap- 
sules are  thicker,  and  contain  red  granules. 

MOLLUSCA.  In  Tunicata  function  of  hearing  is  assigned 
to  a  capsule  containing  calcareous  bodies  lying  beneath  the 
nerve  mass. — In  Lamellibranchiata  the  ear  is  placed  near  foot, 
when  present.  The  capsule  is  elastic,  opaque,  tenacious,  and 
contains  a  circular  commonly  motile  otolithe. — In  Gastero- 
poda the  ears  (two  in  number)  are  often  situated  upon  pe- 
riphery of  body  at  the  sides  and  beneath  the  oesophageal  ring, 
less  frequently  above  it.  The  otolithes,  as  a  rule,  are  numer- 
ous, motile,  and  composed  of  carbonate  of  lime. — In  Ceph- 
alopoda the  ear-chambers  (two  in  number)  are  lodged  in  the 
lower  middle  portion  of  the  cephalic  cartilage,  where  they 
form  two  more  or  less  large,  rounded  cavities,  separated 
by  a  cartilaginous  septum,  and  without  any  external  com- 
munication. (Siebold.)  Each  chamber  holds  in  relation  to 
its  walls,  by  delicate  fibrous  threads,  an  otic  capsule  con- 
taining a  soft  calcareous  otolithe. 

ARTICULATA.  Annelida,  in  Torrea,  possess  distinct  audi- 
tory capsules. — In  Crustacea  and  Insecta  the  organ,  as  a  rule, 
is  appended  to  the  basal  segment  of  one  of  the  anterior  ex- 
tremities. The  capsule  may  be  completely  enclosed  within 
the  calcareous  walls  of  the  segment,  as  in  Lucifer;  or  the  an- 
terior portion  of  the  capsule  maybe  exposed,  as  in  Crustacea 
and  Insecta  generally.  In  Horwrus  (lobster)  the  membrane 
is  open,  and  permits  siliceous  particles  to  enter  from  without 
to  assume  the  functions  of  otolithes.  They  rest  upon  a  num- 
ber of  hair-like  points  fixed  to  the  bottom  of  the  sac.  In 
Palcemon  anterior  membranous  portion  of  sac  is  fissured; 
and  the  single  ovoidal  otolithe  rests  upon  the  extremities  of 
hair-like  processes  projecting  from  basal  surface  of  capsule. 

7 


98  COMPARATIVE   ANATOMY. 

VERTEBRATA.  Organ  divided  for  convenience  into  inter- 
nal, middle,  and  external  ears. 

The  internal  ear  (labyrinth)  is  the  true  otic  capsule,  and 
corresponds  to  the  ear  of  Invertebrata.  It  is  constantly  di- 
vided into  vestibule  (sacculus)  and  semicircular  canals;  and 
in  all  Yertebrata  above  cartilaginous  fishes  is  enclosed  in  an 
osseous  case  composed  of  three  bones,  named  pro-otic,  epi- 
otic,  and  opisthotic.  It  may  be  entirely  closed,  as  in  fishes 
and  perennibranchiate  batrachians,  or  present  a  single  orifice 
anteriorly  (fenestra  oralis),  which  may  be  occupied  by  end  of 
columnella,  or  stapes.  When  the  cochlea  (which  is  recog- 
nized as  a  modified  semicircular  canal)  is  added,  a  second 
opening  (fenestra  rotundum)  is  seen,  which  is  covered  by  mem- 
brane. Otolithic  contents  commonly  present. — The  middle 
ear  (cavity  of  tympanum)  is  a  chamber  placed  in  advance  of 
otic  capsule,  and  defined  within  by  its  anterior  portion,  with- 
out by  the  tympanic  membrane.  It  is  lined  with  mucous 
membrane,  communicates  with  pharynx  through  Eustachian 
tube,  and  is  traversed  by  a  single  bone  (Batrachia,  Eeptilia, 
and  Aves),  or  a  chain  of  bones  (Mammalia). — The  external 
ear  is  all  that  portion  beyond  the  middle  ear.  It  is  divided 
into  an  external  auditory  canal  (meatus)  and  an  auricle 
(conch). 

Pisces. — In  Amphioxus  and  marsipobranchiate  fishes,  ear 
enclosed  within  cranial  walls;  semicircular  canals  two  in 
number,  not  distinct ;  otolithes  absent.  In  Myxine  the  cap- 
sule is  a  single  circular  canal.  In  Raidse,  auditory  sac,  em- 
bedded in  walls  of  cranium,  communicates  with  the  exterior 
by  several  openings,  and  contains  a  quantity  of  gritty  matter; 
otolithes  less  dense  than  in  osseous  fishes. — In  osseous  fishes 
the  ear  is  enclosed  in  a  bony  envelope.  The  semicircular 
canals  are  always  three  in  number.  The  main  body  of  cap- 
sule (vestibule)  contains  a  large  otolithe  nearly  filling  the 
chamber:  no  communication  seen  with  either  pharynx  or 
integument.  With  some  fishes  the  labyrinth  is  extended  by 
a  portion  which  unites  with  that  of  the  opposite  side,  and 
afterward,  on  the  outside  of  the  occiput,  to  terminate  in  a 
chamber  on  the  first  vertebra.  Here,  by  means  of  a  small 


SPECIAL   ORGANS.  99 

chain  of  bones,  it  is  brought  in  connection  with  the  swim 
bladder,  so  that  by  this  arrangement  the  intensity  of  the 
vibrations  of  sound  is  augmented.  In  other  osseous  fishes, 
as  in  Cottus,  the  swim  bladder  extends,  without  such  a  chain 
of  bones,  to  membranous  spaces  in  cranium  which  are  in 
connection  with  the  auditory  apparatus.  (Van  der  Hoeven.) 

Batrachia. — Internal  ear  based  upon  same  plan  as  in  Pisces; 
vestibule,  however,  is  proportionately  smaller.  In  Proteus 
(perennibranchiate)  it  is  imperfectly,  but  in  Rana  (caduci- 
branchiate)  completely  embedded  in  otic  bones.  Otolithes 
granular.  Middle  ear  absent  in  aquatic  types,  as  in  Proteus; 
rudimentary  in  others.  Generally  remote,  the  mouths  of 
Eustachian  tubes  sometimes  unite  in  middle  of  palate.  Tym- 
panic ossicle  (columnella)  single.  Tympanic  membrane  on 
side  of  head  in  Rana. 

Reptilia. — Internal  ear  completely  enclosed  within  otic 
bones.  Cochlea  present, — rudimentary,  slightly  curved,  not 
divided  by  internal  lamina  (scala)  except  in  Crocodilia.  Oto- 
lithes in  Ophidia  dense, — in  Chelonia  and  Sauria  softer.^— 
Middle  ear  larger  in  Sauria  than  Ophidia;  traversed  by 
columnella,  and  covered  externally  by  a  thin,  transparent, 
naked  membranous  continuation  of  the  skin  placed  on  a 
level  with  general  surface  of  head,  or  slightly  projected,  as  in 
Crocodilia.  (Grant.)  In  Ophidia  the  tympanic  membrane  is 
covered  by  skin  and  muscles. 

Aves. — Internal  ear  with  narrow  vestibule ;  cochlea  curved, 
and,  assuming  the  form  of  the  spiral,  is  divided  internally 
by  lamina.  Semicircular  canals  long  and  narrow  in  ra- 
pacious birds,  large  and  wide  in  singing  birds.  Otolithes 
small. — Middle  ear  traversed  by  columnella  and  vidian  nerve. 
Eustachian  tubes  commonly  unite  before  they  open  into  pos- 
terior nares.  Walls  of  cavity  pierced  by  several  foramina 
which  lead  to  large  cells  between  two  tables  of  skull. — Ex- 
ternal ear  present  in  most  birds  in  the  form  of  a  crescentic 
fold  of  skin  extending  upward  from  the  superior  margin  of 
the  external  meatus.  (Grant.) 

Mammalia. — Internal  ear  with  vestibule  comparatively 
small.  Cochlea,  excepting  in  Ornithorhynchus  (duck-bill), 


100  COMPARATIVE   ANATOMY. 

where  it  resembles  that  of  the  bird,  is  a  large  heliciform 
chamber  abundantly  supplied  with  filaments  of  the  acoustic 
nerve,  and  divided  longitudinally  by  a  solid  lamina.  Otolithes 
granular. — Middle  ear  traversed  by  chain  of  bones  called, 
from  within  outwards,  stapes,  incus,  and  maleus.  The  vidian 
nerve  escapes  through  tympanum,  as  in  Aves.  Communica- 
tion with  diploe  is  seen  in  the  openings  between  the  middle 
of  the  ear  and  mastoid  process. 

The  temporal  bone  of  mammals  is  divided  into  three  por- 
tions— squamous,  mastoid,  and  petrous — and  is  usually  de- 
scribed as  arising  from  six  centres  of  ossification :  squamous, 
t}7mpanic,  zygomatic,  styloid,  mastoid,  and  petrous.  But  the 
petrous  portion  in  reality  arises  from  two  distinct  centres  of 
ossification  (opisthotic  and  pro-otic),  the  mastoid  (epi-otic)  in 
part  only  from  one. 

In  the  human  skull  the  petrous  portion  of  the  bone,  as 
thus  formed,  is  a  very  complicated  adjustment  of  bony  ele- 
ments, viz.:  an  inferior  opisthotic  bone  containing  the  lower 
part  of  cochlea,  and  a  superior,  pro-otic,  sheltering  the  greater 
part  of  the  vestibule,  the  upper  part  of  the  cochlea,  the  an- 
terior vertical  semicircular  canal,  part  of  the  posterior  verti- 
cal canal,  and  the  external  semicircular  canal.  (Huxley.)  The 
epi-otic  is  confined  entirely  to  the  mastoid  process.* 

Monotremata. — Cochlea  smaller  than  in  other  mammals ; 
semicircular  canals  relatively  large.  Tympanic  ossicles  an- 
chylosed,  resembling  columnella  of  reptiles  and  birds.  In 
Echidna  (porcupine  anteater)  external  auditory  canal  long  and 
wavy. 

Marsupialia. — The  middle  ear  often  extends  into  petrous 
portion  of  temporal  and  bod}7  of  sphenoid  bones. 

Eodentia. — Bony  portion  of  external  auditory  canal  often 
extended,  and  directed  backwards,  as  in  Lepus  (hare). 

*  Although  in  man  the  tympanic  bone  becomes  early  united  with  the  squa- 
mous, it  remains  separate  from  it  in  many  of  the  lower  animals ;  in  some  of 
these,  as  in  Cetacea,  it  is  joined  to  the  petrous  and  mastoid,  and  forms,  with 
them  and  the  styloid,  a  bone  which  continues  distinct  from  the  squamous. 
The  mastoid  portion  remains  quite  separate  in  some  animals,  and  occasion- 
ally, though  very  rarely,  in  the  human  skull.  (Humphrey.) 


SEXUAL    CHARACTERS.  101 

CetacecL — Tympanic  membrane  plicated.  External  audi- 
tory canal  long,  narrow,  flexible. 

Carnivora,  Insectivora,  and  Cheiroptera. — External  auditory 
canal  apt  to  be  inflated  at  base,  forming  a  conspicuous  con- 
vexity beneath  on  base  of  skull.  The  remainder  of  canal  is 
membranous. 

Quadrumana. — The  external  auditory  canal  entirely  mem- 
branous in  New  World  monkeys. 

Auricle  or  external  ear  is  absent  in  Cetacea,  rudimentary  in 
Phoca  (seal),  and  is  rudimentary  generally  in  aquatic  animals, 
as  Lutra  (otter),  or  in  certain  burrowers,  as  Talpa  (mole). 
With  terrestrial  mammals  it  attains  its  greatest  development. 
Commonly  employed  in  collecting  serial  vibrations,  it  at  times 
serves  as  an  organ  of  touch,  as  in  Corynorhinus. 


XIV. 

SEXUAL  CEABACTERS, 

THE  reproductive  function  profoundly  modifies  the  nutri- 
tive processes  of  the  organism.  The  results  of  such  modifi- 
cations furnish  the  basis  for  sexual  characters.  In  the  higher 
animals  the  sexes  can  be  separated  by  organs  of  generation 
constantly  present.  The  tout  ensemble  of  sexual  characters 
here  pertain  less  to  the  organs  than  to  the  influence  exerted 
by  them  upon  the  whole  economy.  But  in  many  lower  ani- 
mals the  power  thus  exerted  by  the  organs  over  the  general 
appearance  of  the  animal  is  less  evident,  and  with  some  it  is 
entirely  absent.  With  the  coelenterate  radiates,  for  example, 
sex  can  be  distinguished  only  by  the  increased  growth  of  the 
organs  during  periods  of  procreation.  Indeed,  in  Hydra  the 
organs  do  not  appear  at  any  other  time. 

Sexual  characters  are  general  and  special.  (1)  General 
characters  are  those  maintained  throughout  life,  and  are  best 


102  COMPARATIVE   ANATOMY. 

pronounced  at  maturity.    (2)  Special  characters  are  those  pe- 
culiar to  times  of  procreation  and  rearing  of  young. 

(1)  Size. — With  Invertebrata the  female  is  the  larger;  with 
the  Vertebrata  the  reverse  is  true  as  a  rule.  In  species  where 
the  female  carries  large  numbers  of  eggs  within  her  tissues, 
either  preparatory  to  ovi-position  or  throughout  development, 
their  accommodation  and  support  necessitate  extensive  growth 
and  active  nutrition.  Such  females  are  always  larger  than  the 
corresponding  males.  Examples  are  found  in  many  nematoid 
Entozoa,  some  rotifers,  as  in  Asplanchna,  in  Argonauta  (paper 
nautilus),  and  in  many  insects,  as  particularly  seen  in  Termes 
(termite  ant).* 

Special  organs. — Special  organs  may  be  divided  into  those 
(a)  for  the  attraction  of  the  opposite  sex,  such  as  luminous 
organs  of  Photinus  scintillans  (small  firefly) ;  vibratory,  stridu- 
lous  organs,  as  in  Gryllus  (cricket),  where  certain  nervules  of 
the  anterior  wings  rasp  against  one  another ;  or,  as  in  Cicada 
(American  locust),  where  a  cavity  placed  upon  either  side  of 
the  last  thoracic  segment  is  covered  in  by  a  tympanic  mem- 
brane which  is  rendered  tense  and  vibratory  by  muscular 
action;  (b)  for  retention  of  the  female  in  coitus,  such  as  the 
claspers  in  Squalus  (shark),  where  they  are  placed  one  on 
either  side  of  the  position  of  the  genital  pores; — or  in  the 
sternal  plates  and  finger-like  appendages  to  front  feet,  as  in 
a  genus  of  Batrachia  (Cystignathus)-,  (c)  other  characters,  as 
spur  of  Gallus  (cock),  and  Ornithorhynchus  (duck-bill). — Pecu- 
liarities of  existing  structures,  as  seen  in  growth  of  hair  on  pubes 
and  face  (man), — on  neck  (lion) ; — or  in  modifications  of  voice 
due  to  changes  not  fully  appreciated. 

(2)  Increased  functional  activity: — as  in  pigment  cells  of  ova- 
ries of  Toxopneustes  (sea-urchin), — in  color  of  fins  in  Cypri- 
noid  fishes,  $, — in  plumage  and  wattles  of  birds,  $  9:—  as 
in  secretion  of  the  cervical  gland  of  Crocodile,  1 , — sebaceous 
gland  of  penis  of  Anser  (goose),  fc , — labial  gland  of  Camelus 
(camel),  $ ; — testicles  and  ovaries  of  Aves, — and  in  the  "moult- 

*  In  some  animals,  us  certain  Cynipidce  (gallflies),  and  some  entomostracan 
crustaceans,  the  male  is  unknown. 


REPRODUCTIVE   SYSTEM.  103 

ing'  of  feathers : — in  increase  of  size  of  mammse,  9 : — in  pe- 
riodic discharge  of  ova,  as  in  Yertebrata  (egg-laying  reptiles 
and  birds), — or  accompanied  with  turgescence  of  organs  of 
generation  (mammalia). — Structural  changes: — as  swollen  shell 
for  protection  of  eggs,  Unio  (mussel),  9 : — in  development  of 
sculptured  capsule  for  eggs,  Argonauta  (paper  nautilus)  9; — 
in  webbed  foot  and  dorsal  fold  of  Salamander,  $; — in  the 
greater  development  of  thumb  of  Eana  (frog),  £;  in  the 
growth  of  antlers,  Cervus  (deer)  $; — changes  in  larynx  in 
certain  birds  producing  song,  £ . 


XV. 

BEPBODUCTIVE  SYSTEM, 

THE  reproductive  system  is  composed  of  the  organs  of  gen- 
eration, and  is  devoted  to  the  development  and  retention  of 
the  sexual  elements.  These  are  sperm  cell  and  ovum. 

SPERM   CELL. 

Enclosed  within  the  sperm  cell  are  very  generally  a  num- 
ber of  other  cells  (daughter  cells,  vesicles  of  evolution),  within 
which,  in  turn,  spermatozoa  (spermatic  filaments)  are  devel- 
oped. Each  spermatozoon,  as  a  rule,  is  formed  in  the  same 
vesicle  of  evolution  with  many  others,  though  occasionally 
singly,  as  in  nematoid  Entozoa.  Very  generally  the  result 
of  an  obscure  transformation  of  the  contents  of  the  daughter 
cell,  the  spermatozoon  may  be  a  modified  nucleus, — or  less 
frequently  the  transformed  cell  itself,  as  in  decapod  crus- 
taceans. 

The  forms  of  spermatozoa  are  exceedingly  various.  The 
principal  ones  are  as  follows:  slender  filament,  with  ovoidal 
expansion  at  one  extremity;  this  expansion  oval,  acumi- 
nate, as  in  man;  flat  and  obtuse  in  Sciurus  (squirrel);  sickle- 
shape,  as  in  Mas  (rat);  pyriform,  as  in  Canis  (dog);  verm- 


104  COMPAKATIVE   ANATOMY. 

iform,  with  fine  hair-like  tail,  as  in  Aves  and  Reptilia; 
staff-shaped  expansion,  with  short  filament  often  coiled  upon 
itself,  as  in  Batrachia  generally;  globular,  as  in  osseous 
fishes ;  vermiform,  as  in  marsipobranehiate,  elasmobranchiate 
fishes,  and  cephalopodous  molluscs; — and  acuminate-oval 
with  long  filament,  as  in  Helix  (snail),  with  short  cylindrical 
or  pyriform  fibres,  as  in  Unio  (mussel).  In  Nepa  the  expan- 
sion is  slight,  and  filament  long, — cylindrical  in  Epeira  (spi- 
der),— pyramidal,  with  concave  sides  in  Julus, — or  of  a  gro- 
tesque shape,  with  central  body  and  radiatory  filaments,  as  in 
Homarus  (lobster),  and  other  decapod  crustaceans.  In  Onis- 
cus  (pillbug),  the  spermatic  filaments  are  large  enough  to  be 
seen  by  the  naked  eye. — The  quantity  is  at  all  times  greatly 
in  excess  of  the  number  of  eggs  actually  impregnated.  It  is 
estimated  that  in  a  drachm  of  human  semen  more  spermatic 
filaments  are  contained  than  there  are  people  in  the  world. 

OVUM. 

The  ovum  (egg)  is  the  product  of  parental  sexual  genera- 
tion from  which  the  young  of  animals  are  produced.  (Thom- 
son.) 

The  simplest  expression  of  the  egg  is  a  sphere  with  faintly 
granular  contents,  as  in  Stentor.  It  may  present  two  concen- 
tric spheres,  as  in  Laomedea;  or  in  the  higher  animals,  as 
most  molluscs,  articulates  and  vertebrates,  three  concentric 
spheres,  called  after  their  position  from  within  outward,  nu- 
cleolus, — germinal  spot  (nucleus,  Wagnerian  vesicle), — and 
germinal  vesicle  (germ  cell,  vesicle  of  Purkinje). 

Every  egg  is  composed  of  an  albuminous  and  oleaginous 
substance.  The  first  of  these  is  on  the  side  of  the  ovum 
with  the  germinal  spot  and  vesicle,  which  is  hence  called  the 
germinal  area ;  the  second  is  upon  the  opposite  side,  and  is 
known  as  the  yolk  (vitellus).  Ordinarily  the  yolk  is  formed 
with  germinal  vesicle  in  ovary,  but  in  Holothuria  (sea-cucum- 
ber) and  in  certain  Entozoa  (q.v.)  distinct  appendages  (yolk 
glands)  to  the  oviduct  are  reserved  for  this  purpose. 

The  egg  becomes  impregnated  by  the  entrance  of  one  or 


REPRODUCTIVE    SYSTEM.  105 

more  spermatozoa.  These  may  be  lost  within  investing  mem- 
brane, or  gain  access  to  the  germinative  area  through  a 
special  opening  (micropyle). 

The  first  evidences  of  impregnation  are  disappearance  of 
the  germinal  vesicle  and  spot,  when  present,*  and  the  seg- 
mentation of  the  vitellus,  forming  the  mulberry  mass.  Seg- 
mentation may  be  partial,  as  in  Aves,  or  complete,  as  in 
Annelides. 

The  unsegmented  yolk  is  designed  for  the  nourishment  of 
the  embryo  during  incubation,  and  bears  fixed  relations  to 
the  conditions  surrounding  the  impregnated  egg  and  to  the 
time  occupied  in  the  evolution  of  the  embryo.  Where  ova 
are  retained  in  connection  with,  and  are  nourished  through 
the  tissues  of  the  mother  (gestation),  as  in  Mammalia,  or 
where  they  are  early  discharged  from  the  mother,  and  devel- 
opment to  a  self-supporting  stage  proceeds  rapidly,  as  in  Pro- 
tozoa, Radiata,  Entozoa,  and  most  Mollusca,  little  or  no  vitel- 
lus is  required.  Such  examples  compose  the  first  group  of 
eggs,  characterized  as  follows:  Eggs,  for  the  most  part  of 
small  size,  often  very  minute;  the  yolk  substance  entirely 
composed  of  elementary  granules  or  minute  and  simple 
spherules;  the  process  of  segmentation  affecting  the  whole 
mass  of  the  yolk,  and  the  germinal  layer,  resulting  from  that 
segmentation,  extending  from  the  first  over  the  whole  sur- 
face of  the  ovum.  The  whole  yolk  is  germinal,  or  con- 
verted into  the  parts  of  the  future  embryo. — In  the  second 
group,  the  great  majority  of  which  are  oviparous,  the  ova  are 
proportionately  of  the  largest  size.  The  yolk  substance  con- 
sists very  obviously  of  two  kinds  of  organized  particles,  viz., 
of  small  granules,  nearly  similar  to  those  which  form  the 
whole  yolk  in  the  last  group,  and  which  alone  undergo  seg- 
mentation, large  cells,  usually  non-nucleated,  and  fat  vesi- 
cles, which  constitute  the  greater  part  of  the  mass.  The  first 
of  these  enter  into  the  germinative  area,  the  second — the 
part  making  up  the  great  bulk  of  the  egg — is  strictly  nutri- 

*  Rarely  the  germinal  spot  and  vesicle  are  not  lost  after  conception, 
but  the  germinal  vesicle  itself  undergoes  segmentation,  as  in  Ascaris  mystax. 
(Nelson.) 


106  COMPARATIVE   ANATOMY. 

tive.  Such  eggs  are  met  with  in  Aves,  Reptilia,  cartilaginous 
fishes,  and  perhaps  also  in  Cephalopoda  and  a  few  other 
invertebrates. — In  the  third  group,  the  yolk  is  of  medium 
size  and  composed  of  two  kinds  of  granules.  But  the  nutri- 
tive are  but  fe.w  in  number  and  are  subject  to  considerable 
variety;  the  greater  part  of  the  mass  undergoing  segmenta- 
tion. Within  this  group  are  included  the  eggs  of  osseous 
fishes,  Batrachia,  the  higher  Crustacea,  Arachnida  and  In- 
secta.  (Thomson.) 

The  egg  is  generally  spherical,  though  occasionally  oval,  as 
in  Sepia.  The  shell  is  commonly  smooth,  as  in  Yertebrata, 
but  may  present  many  curious  tubercular,  fringed  or  spinous 
processes,  as  in  Insecta.  In  Polyzoa  the  egg  is  often  fur- 
nished with  bifid  hooks,  as  in  Plumatella. 

The  investing  membrane  of  egg  is  termed  the  chorion. 
It  may  be  shaggy,  as  in  Mammalia,  or  smooth,  as  in  all 
others.  In  eggs  of  the  second  group  the  chorion  (membrana 
putaminis)  is  divided  into  two  layers,  the  outer  one  lining 
the  shell,  the  inner  one  enclosing  the  albumen  (white  of  egg). 
At  the  '  butt'  of  the  egg  the  two  layers  are  wide  apart,  con- 
stituting the  'air  chamber.'  Within  the  albumen  a  chala- 
ziferous  membrane  is  found — forming  the  'chalaza' — upon 
either  pole  of  the  vitellus.  Immediately  surrounding  the 
vitellus  is  a  diaphanous  vitelline  membrane.  The '  egg  shell' 
may  be  composed  of  carbonate  of  lime,  as  in  certain  Entozoa, 
Helix,  and  oviparous  vertebrates ;  or  one  of  various  kinds  of 
coriaceous  and  chitinous  structures. 

The  number  of  eggs  varies  greatly  in  different  animals.  As 
a  rule,  it  bears  a  direct  proportion  to  the  risks  attending  de- 
velopment. Where  the  ova  are  well  protected  during  gesta- 
tion, as  in  the  placental  mammal,  a  few  only  escape  at  a  time, 
and  with  many  animals,  as  the  human  female,  the  number 
is  restricted  to  one.  With  aquatic  forms,  on  the  other  hand, 
the  eggs  may  lie  unprotected  during  gestation.  Great  num- 
bers are,  in  consequence,  consumed  by  carnivorous  animals, 
become  infected  with  parasites,  or  may  otherwise  fail  to  attain 


REPRODUCTIVE    SYSTEM.  107 

maturity  by  the  frequent  modifications  occurring  in  the  ac- 
companying conditions  of  life.  Were  no  provision  made  for 
these  inevitable  losses,  species  so  propagating  would  be  in 
danger  of  extinction ;  a  result,  however,  ordinarily  precluded 
by  the  enormous  number  of  eggs  deposited  at  each  sexual 
period.  It  is  estimated  that  at  such  times  a  single  female 
cod  will  discharge  from  4,000,000  to  9,000,000  eggs,  Doris, 
600,000,  and  Gordius  (hair-worm),  6,000,000.  In  Tcenia  (tape- 
worm), 200  eggs  can  be  counted  within  each  segment. 

Eggs  are  disposed  of  in  various  ways.  In  Fulgur  (whelk) 
they  are  contained  within  disks, — composed  of  a  hardened 
secretion  from  oviduct, — which  are  loosely  connected  longi- 
tudinally. In  Sepia  (cuttlefish),  each  of  the  clustered  egg- 
capsules  (marine  grapes)  contains  from  twenty  to  thirty  ova. 
The  capsules  of  Doris  assume  the  form  of  long  lace-like 
bands;  those  of  Janthina  that  of  a  conoidal  raft  which  remains 
attached  to  parent;  those  of  elasmobranchiate  fishes,  quad- 
rate, tray-like  figures  with  long,  prehensile  tendrils  pendent 
from  angles.  During  development  of  eggs  of  oviparous 
forms,  they  are  either  set  entirely  free  and  remain  unpro- 
tected, as  in  most  aquatic  animals,  or  are  covered  by  the 
female,  as  in  the  majority  of  birds.  In  the  former  case 
they  may  be  agglutinated  in  an  albuminous  product  of  the 
oviduct,  as  in  fresh-water  Gasteropoda  and  Batrachia.  In 
osseous  fishes  they  are  often  cast  into  grooves  in  the  sand 
(ridds).  In  Insecta  they  may  be  placed  through  ovipositors 
in  localities  where,  during  the  larval  condition,  the  most  ap- 
propriate nourishment  can  be  procured  for  the  embryo,  as  in 
Apis  (bee),  or  where  the  larva  can  best  procure  its  own  food, 
as  in  Cynips  (gall-fly). 

Eggs  are  often  carried  by  parent,  viz.:  in  the  marginal 
pouches  of  discophorous  Acalephse  (jelly-fishes), — between 
the  gills  of  Unio  (mussel), — within  the  peculiar  shell  of  Ar* 
gonauta  (paper  nautilus), — to  the  sides  of  entomostracan 
crustaceans,  as  Cyclops, — or  beneath  the  tail  segments  of 
Homarus  (lobster).  They  are  at  times  secured  to  the  skin 
of  abdomen,  each  by  a  separate  pedicle,  as  in  Aspredo  icevis 


108  COMPARATIVE    ANATOMY. 

(Surinam  catfish),  or  Hylodes  lineatus  (Surinam  frog).  En- 
twined in  a  figure-of-eight  coil  around  the  hind  legs,  as  in 
Alytes  obstetricanS)  they  may  be  contained  within  a  large  cuta- 
neous dorsal  fold  opening  posteriorly  at  coccyx,  as  in  Osteo- 
cephalus.  Among  fishes  they  may  be  held  in  a  pouch  near 
anus,  as  in  the  male  of  Hippocampus  (sea-horse),  or  in  the 
mouth  of  the  male  of  Bagrus. 

The  oviduct  may  retain  the  egg  during  a  portion  of  the 
time  required  for  development,  as  in  Chelonia,  implacental 
mammals,  or  during  the  whole  of  it,  as  in  Paludina  vivipara, 
Anableps,  Ditrema  argenteum,  Blennius  (blenny),  the  innocent 
serpents,  and  placental  mammals.  Such  animals  are  called 
for  convenience  viviparous. 

The  placenta  is  a  structure  peculiar  to  placental  mammals 
(see  classification,  and  p.  134).  Placenta-like  structures  seen 
in  some  nematoid  Entozoa; — Salpa;  Squalus  (shark),  and  an 
osseous  fish,  Ditrema  argentewn.  In  implacental  mammals  the 
embryo  is  discharged  at  an  early  stage  of  development  to  be 
attached  to  mammary  gland  within  an  inguinal  pouch,  as  in 
Marsupialia,  or,  in  absence  of  pouch,  after  a  manner  imper- 
fectly understood,  as  in  Monotremata. 

The  act  of  an  egg  at  maturity  escaping  from  the  ovary  is 
termed  ovulatlon.  The  time  of  its  occurrence  varies  in  dif- 
ferent animals.  In  a  majority  of  species  the  act  is  repeated 
for  a  number  of  years  consecutively,  generally  in  the  spring, 
in  terrestrial  animals,  and  frequently  several  times  a  year; 
most  of  the  lower  animals,  however,  lay  eggs  in  the  fall,  or 
during  winter.  In  others,  on  the  contrary,  it  occurs  but  once 
during  life,  at  the  period  of  maturity,  and  the  animal  soon 
afterward  dies.  (Agassiz  and  Gould.)  Ovulation  is  frequently 
accompanied  with  sexual  excitement  (see  sexual  characters, 
p.  102).  In  Mammalia  it  induces  a  determination  of  blood 
to  the  genital  organs  of  the  female,  accompanied  by  sexual 
desire.  This  is  termed  'rut'  in  the  deer,  boar,  etc.,  and 
'heat'  with  carnivores.*  Phenomena  of  menstruation  con- 
fined to  Quadrumana  and  the  human  species. 

*  The  heat  belongs  more  properly  to  the  female  than  to  the  male,  as  there 
are  many  species  whose  females  receive  the  male  only  at  particular  seasons, 


REPRODUCTIVE  SYSTEM.  109 


ORGANS  OF  GENERATION. 

Testicle. — A  circumscribed  collection  of  sperm  cells  is  called 
a  testicle.  Its  cells  are  free,  as  in  Tethya,  or  arranged  loosely 
to  one  another  between  folds  of  membrane — peritoneal  or 
otherwise,  as  in  most  Radiata  and  marsipobranchiate  fishes ; 
or  line  either  straight  or  convoluted  follicles,  as  in  most  Mol- 
lusca,  Articulata,  and  Yertebrata.  In  the  first  two  groups 
the  filaments  are  discharged  adventitiously  without  duct,  i.e. 
by  bursting  through  capsule  of  organ.  In  the  majority  of  the 
last  they  pass  along  a  well-defined  and  commonly  tortuous 
canal  (vas  deferens),  which  opens  by  an  independent  point 
(genital  pore),  as  in  cartilaginous  fishes  and  most  Inverte- 
brata,  or  joins  urethra  near  its  termination,  as  in  the  majority 
of  Vertebrata.  The  appendages  to  such  a  canal,  when  present, 
may  be  follicular  (urethral),  convoluted  (vesiculse  seminales), 
racemose  (prostate  body  and  glands  of  Cowper). 

Ovary. — A  circumscribed  collection  of  ova  is  called  an 
ovary.  It  bears  a  marked  external  resemblance  to  testicle 
when  cells  are  free,  as  in  Tethya, — or  loosely  held  together 
without  oviduct  between  festoons  of  membrane,  as  in  Ra- 
diata and  marsipobranchiate  fishes.  The  resemblance  is  less 
decided  when  the  cells  partially  or  entirely  line  the  blind  ex- 
tremity of  a  tube,  the  contracted  continuation  of  which  forms 
the  oviduct,  as  in  majority  of  osseous  fishes, — or  where  the 
cells  are  supported  by  a  distinct  cellular  or  fibrous  stroma 
distinct  from  oviduct,  as  in  other  Yertebrata.  In  Yertebrata 
each  oviduct  may  unite  with  its  fellow  in  median  line,  as  in 
Mammalia,  or  continue  to  outlet  separately,  as  in  others. 

"When  an  organism  possesses  both  sexual  elements  it  is 
said  to  be  hermaphroditic  (bi-sexual,  monoecious,  androgy. 
nous),  when  one  cell  only  unisexual  (dioecious).  Although 

whilst  the  male  is  at  all  times  fit  for  propagation.  In  others,  constituting 
the  majority  of  instances,  the  male  organs  are  subject  to  the  same  periodical 
increase  of  activity  as  the  female.  The  male  in  these  animals  is  usually  in 
heat  at  an  earlier  period  than  the  female.  (Thomson.) 


110  COMPARATIVE   ANATOMY. 

within  every  hermaphroditic  animal  two  essential  elements 
of  generation  are  contained,  few  animals  possess  the  power 
of  self-impregnation.  Such  are  Hydra,  Holothuria,  solitary 
Ascidians,  and,  probably  animals  developing  by  encapsula- 
tion (q.  v.). 

The  union  of  cell-products  results  in  impregnation  of  ovum. 
This  may  occur  outside  the  body,  as  in  certain  annelides, 
molluscs,  and  fishes;  or  just  within  the  mouth  of  the  ovi- 
duct by  adaptation  of  parts  (coitus),  as  in  the  majority  of 
animals.  Coitus  may  be  simply  the  contact  of  the  mouths 
of  the  seminal  and  oviducts,  or  penetration  of  the  latter  by 
means  of  an  intromittent  organ  (penis). 

PROTOZOA.  Animals,  so  far  as  known,  hermaphroditic. 
In  Tethya  spermatic  filaments  and  ova  lie  side  by  side,;  no 
ducts.  In  Paramecium  the  '  nucleus'  represents  the  ovary,  the 
'nucleolus'  the  testicle;  no  ducts.  Reciprocal  transmission 
of  spermatic  filaments  takes  place  through  the  oral  openings. 

RADIATA.  The  sexual  organs  resemble  one  another  so 
closely  that,  excepting  at  times  of  procreation,  they  cannot 
be  distinguished,  and  even  then  only  by  their  minute  struc- 
ture. They  may  be  developed  in  the  indifferent  tissue  of 
body,  as  in  Hydra,  or  appended  to  the  inner  edge  of  the  body, 
as  in  Actinia.  Their  contents,  as  a  rule,  escape  by  the  diges- 
tive cavity.  Polypi  may  be  hermaphroditic,  as  in  Hydra,  or 
unisexual,  as  in  Actinia.  In  Acalephse  the  genital  organs  are 
not  developed,  except  at  the  time  of  procreation,  and  this 
period  is  very  brief.  The  organs  consist  either  of  elongated 
pouches  or  ribbon-like  bands,  which  are  situated  in  different 
parts  of  the  body.  In  the  first,  sperm  and  eggs  escape 
through  particular  excretory  canals ;  in  the  second,  they  es- 
cape directly  outward  from  the  ovaries  or  pass  through  large 
cavities  which  communicate.  In  Hydroida  the  organs  are 
rarely  found  upon  hydroid  stock,  as  in  Rhizogeton ;  more  often 
they  are  arranged  in  the  form  of  brilliantly-colored  rays  be- 
neath umbrella-like  expansion  of  medusa  bud. 

Echinodermata. —  Generally  unisexual.  Holothuria  and 
Synapta  exceptions.  In  Toxopneustes  (sea-urchin)  the  posi- 


REPRODUCTIVE    SYSTEM.  Ill 

tion  of  reproductive  organs  varies;  each  organ  is  composed 
of  simple  or  branched  tubes,  with  proper  excretory  ducts; 
these  last  are  sometimes  wanting,  when  the  contents  of  the 
former  escape  by  rupture,  and,  falling  into  the  cavity  of 
the  body,  pass  out  through  the  respiratory  openings.  (Sie- 
bold.)  Copulatory  organs  absent.  In  Toxopneustes  (sea- 
urchin)  the  organs  fill  up  the  interspaces  between  rows  of 
ambulacral  vesicles.  Holothuria  is  bi-sexual.  The  ovary  is  in 
the  form  of  slender  tubes  floating  freely  in  the  cavity  of  the 
body,  the  efferent  canal  (oviduct)  opens  upon  the  back  in  the 
neighborhood  of  the  mouth,  below  the  osseous  rings,  between 
the  tentacles.  Peculiar  appendages  to  oviduct  seen  in  the 
form  of  so-called  yelk  glands.  Male  apparatus  closely  re- 
sembles the  above.  In  Synapta  the  testes  and  ovaries  are  in 
one  tube;  the  eggs  become  impregnated  by  being  pressed 
against  the  sperm  cells. 

MOLLUSCA.  Polyzoa. — With  the  hermaphroditic  Polyzoa 
a  ribbon-like  ovary  and  testicle  are  suspended  from  the  ex- 
tremity of  the  stomach.  In  these  organs  are  developed  only 
two  to  four  eggs  or  fasciculi  of  spermatic  particles  from  cells 
arranged  like  a  string  of  pearls.  (Siebold.)  The  sexual  ele- 
ments are  probably  voided  through  tentacles. 

Brachiopoda. — In  the  unisexual  Brachiopoda  two  pairs  of 
ovaries  and  testicles  are  developed  between  mantle  and  the 
lining  membrane  of  the  venous  sinus.  The  method  of  escape 
is  unknown. 

Tunicata — The  Tunicata,  excepting  the  solitary  Ascidians 
and  Salpa,  are  hermaphroditic.  The  former  may  be  self-im- 
pregnating. The  organs  are  situated  between  the  branchial 
chamber  and  mantle. 

Lamellibranchiata. — Rarely  hermaphroditic,  as  in  Cyclas. 
The  male  or  female  organ  is  placed  in  relation  with  the  liver, 
and  beneath  the  mantle.  The  oviduct  empties  in  or  about 
the  renal  sac.  When  the  foot  is  largely  developed,  the  testicle 
is  commonly  placed  within  the  interior  of  the  base,  while  the 
vas  deferens,  toward  the  base  of  foot  when  present,  or  near 
mouth,  as  in  Oslrea  (oyster).  ISTo  copulatory  organs. 

Gasteropoda,  —  The   Gasteropoda  may  be   either  herma- 


112  COMPARATIVE   ANATOMY. 

phroditic  or  unisexual.  Of  the  former  Helix  (snail)  is  an 
example ;  of  the  latter,  Paludina.  A  Fallopian  tube  passes 
from  the  ovary,  commonly  lodged  in  or  near  liver,  to  the 
uterine  sac,  at  whose  base  lies  an  albumeniparous  sac,  while 
at  the  point  where  it  is  continuous  with  the  vagina,  a  recep- 
tacle for  semen  is  situated.  The  male  genital  organs  consist  of 
a  testicle,  a  vas  deferens  and  an  ejaculatory  duct,  which  may 
present  a  simple  orifice,  or  open  into  a  retractile  penis  often  of 
great  size.  "With  the  hermaphroditic  species  the  two  kinds 
of  genital  organs  are  more  or  less  blended  together, — the 
testicle  with  the  ovum  and  the  vas  deferens  with  the  Fallo- 
pian tube.  Every  folliculus  is  double,  and  within  the  ex- 
ternal, which  contains  eggs,  an  internal  is  enclosed,  the 
ova  and  sperm  filaments  thus  lying  in  close  juxtaposition. 
Very  often,  also,  the  vagina  is  united  with  the  ejaculatory 
duct,  forming  a  cloaca  into  which  open  several  special  secret- 
ing organs.  Both  male  and  female  organs  are  usually  lined 
with  ciliated  epithelium.  (Siebold.)  The  genital  pores  may 
be  upon  the  right  or  left  side.  Extraordinary  appendages 
are  seen  to  sexual  organs  in  Helix  (snail),  consisting  of  a  sac 
opening  near  the  outlet,  containing  numbers  of  dart-like 
spiculse  which,  under  sexual  excitement  and  immediately 
preceding  coition,  are  successively  ejected. 

In  Pteropoda  the  ovary  and  testicle  are  contained  within 
the  liver  and  appear  to  be  a  single  organ.  In  Phyllirhoe,  a 
genus  of  Heteropoda,  the  outer  part  of  the  single  organ  is 
the  ovary,  the  inner  the  testicle.  The  ova  and  spermatic 
filaments  mingle  within,  and  impregnation  occurs  at  the 
lower  portion  of  the  oviduct. — Penis  of  remarkable  length 
in  Clio. 

Cephalopoda. — The  ovary  is  enclosed  in  a  loose  capsule, 
into  which  from  time  to  time  the  ova  fall,  to  be  conveyed 
thence  through  an  oviduct  emptying  at  base  of  funnel  on  left 
side  of  body  near  rectum.  A  glandular  appendage  furnishes 
accessories  to  the  egg.  Placed  upon  ink-bag  are  two  peculiar 
bodies  (nudimental  glands)  having  a  common  outlet  near  the 
orifice  of  the  oviduct.  They  yield  an  adhesive  substance 
by  which,  after  their  expulsion,  the  eggs  are  fixed  upon 


REPRODUCTIVE   SYSTEM.  113 

submerged  objects. — The  testicle  resembles  in  general  feat- 
ures the  ovary.  The  gland  is  composed  of  numerous  con- 
vergent cylinders ;  is  enclosed  in"  a  loose  membranous  capsule 
from  which  emerges  the  slender  tortuous  vas  defereus.  The 
tube  terminates  in  mantle  near  rectum,  a  small  intromitteut 
organ  protruding.  The  canal  at  lower  portion  is  of  varying 
degrees  of  thickness.  A  single  conspicuous  glandular  body 
(prostate)  and  a  muscular  chamber  (Needham's  pouch)  being 
appended. — This  latter  cavity  is  occupied  by  whitish  filaments 
(spermatophores),  each  having  an  average  length  of  half  an 
inch.  Each  filament  contains  a  convoluted  tube  occupying 
the  greater  part  of  the  cavity,  which  is  filled  with  spermatic 
particles  and  connected  anteriorly  to  a  solid  cylindrical  body 
continuous  behind  with  a  spiral  ligament.  This  latter  is  en- 
closed within  a  thin  sheath  which  is  attached  to  the  end  of 
the  sac.  The  escape  of  the  sperm  from  this  apparatus  is  ef- 
fected during  coition  by  the  rupture  of  the  anterior  extremity 
of  the  filament,  when  the  contents  are  forcibly  ejected  by 
the  action  of  the  spiral  ligament. 

In  Argonauta  (paper  nautilus)  the  male  organs  are  upon  the 
same  type  as  those  already  described,  but  the  manner  by 
which  their  product  effects  union  with  the  female  is  peculiar. 
The  spermatophore  is  lodged  in  the  base  of  one  of  the  arms, 
which,  upon  the  former  becoming  charged  with  filaments,  is 
spontaneously  severed  from  its  connections.  It  now  receives 
the  name  of  the  Hectocotylus,  and  floats  off  in  search  of  the 
female. 

ARTICULATA.     Entozoa. — See  p.  161. 

Rotifera. — Organs  simple.  Ovary  opens  by  oviduct  into 
cloaca.  Male  organs  unknown. 

Annelida. — Genital  apparatus  of  various  forms.  In  Lum- 
bricus  (earthworm),  which  is  hermaphroditic,  the  male  and 
female  organs  resemble  one  another  very  closely.  Their 
orifices  are  situated  in  pairs  upon  the  ventral  surface  at  the 
anterior  extremity  of  the  body,  surrounded  by  a  thickened 
circular  fold  of  integument.  —  The  capitobranchiates  and 
dorsibranchiates  are  of  distinct  sexes.  The  organs  <  which 

o 

project  from  the  ventral  surface  into  the  cavity  of  the  body 


114  COMPARATIVE   ANATOMY. 

between  the  fasciculi  of  the  cutaneous  muscle,'  communi- 
cate with  the  general  visceral  cavity,  the  genital  products 
escaping  thence  through  openings  between  the  feet.  (Siebold.) 

Crustacea.— Generally  unisexual;  hermaphroditic  forms 
are  seen  with  Girripedia. — Male  and  female  organs,  as  a  rule, 
resemble  one  another.  Great  variety  witnessed  in  the  detail 
of  their  arrangement  in  different  families.  The  sexual  ele- 
ments are  placed  within  simple  tubes  arranged  bi-laterally, 
and  with  comparatively  few  exceptions,  open  upon  ventral  sur- 
face of  animal  by  distinct  pores.  At  the  female  genital  pore  a 
special  glandular  canal  is  occasionally  met  with;  a  receptacle 
for  semen  (spermatotheca)  is  rarely  seen. — The  male  pore  is 
commonly  furnished  with  copulatory  organs,  in  the  form  of 
stylets  or  canaliculi,  which  serve  to  transfer  the  sperm  to  the 
female.  To  these  may  be  added  the  'claspers,'  which  are 
more  remotely  placed.  In  Homarus  (lobster),  the  genital 
pore  in  male  is  upon  basal  articulation  of  last  pair  of  ambu- 
latory feet;  in  other  decapods  the  orifice  is  upon  abdominal 
surface  of  last  thoracic  ring.  Copulation  is  common. 

Insecta. — Always  unisexual.  The  genital  organs  are  com- 
posed in  general  of  two  symmetrical  ovaries  or  testicles,  often 
intimately  resembling  one  another,  situated  in  the  abdominal 
cavity,  and  of  two  oviducts  or  deferent  canals,  which  unite  in 
a  common  excretory  duct  opening  back  of  the  anus  or  in  it, 
forming  a  cloaca.  This  duct  has  several  double  or  single 
appendages  of  which  one,  with  the  female,  serves  as  a  sem- 
inal receptacle,  or  as  a  copulatory  organ,  while  the  others,  in 
both  sexes,  are  true  secretory  organs. — In  the  female  the 
vagina  is  often  prolonged  into  an  ovipositor.  This  may  be 
composed  of  segments  which  can  be  drawn  within  one  an- 
other, as  in  Diptera  (fly) ;  or  protected  by  two  valvular  pro- 
jections which  appear  to  prolong  the  body  posteriorly,  as  in 
Locustee  (grasshopper);  or  long,  stout,  and  employed  as 
borer  (tenebra),  as  in  Cynipidse  (gallfly),  slender  and  acu- 
minate, and  employed  as  sting  (aculeus),  as  in  Apidee  (bee). — 
The  same  segment  modified  in  the  male  constitutes  the  penis. 
It  commonly  opens  on  ventrum  at  about  the  ninth  ring. — 
The  seminal  receptacle  is  a  double  or  single  capsule  of  vari- 


REPRODUCTIVE    SYSTEM.  115 

able  form  and  surrounded  by  a  muscular  layer.  It  opens 
into  the  vagina  below  the  point  of  junction  of  the  two  ovi- 
ducts, by  means  of  a  canal  of  variable  length.  The  seminal 
vesicle  is  empty,  except  after  copulation,  when  it  always 
contains  a  multitude  of  spermatozoa  moving  very  actively: 
these  movements  are  kept  up  for  a  long  period.  The  secre- 
tory glands,  situated  at  the  lower  end  of  the  vagina,  con- 
sist of  two  rather  long  glandular  tubes  on  each  side  of  the 
vagina,  into  which  they  open,  either  directly  or  through  two 
small  special  excretory  ducts.  They  often  have  on  their 
course  two  vesiculiform  reservoirs. — The  male  organs  recall 
the  general  plan  of  the  female.  The  vas  deferens,  ordinarily 
simple,  may  have  at  its  lower  extremity  a  vesicular  dilata- 
tion (vesicula  seminalis);  at  their  point  of  junction  on  the 
ejaculatory  duct  there  are  usually  two  longer  or  shorter 
simple  mucous  glands,  which  secrete  a  quickly  coagulating 
granular  mucus,  which  serves,  during  the  copulatory  act, 
partly  to  fill  and  distend  the  copulatory  bursa  and  partly  to 
surround  portions  of  the  sperm,  and  thereby  form  spermato- 
phores.  (Siebold.)  A  variety  of  copulatory  organs  are  seen, 
most  generally  modifications  in  last  segment  of  abdomen  or 
chitinous  deposition  in  terminal  portion  of  vas  deferens,  and 
often  protruded  through  agency  of  complicated  muscular  ap- 
paratus.— "With  Libellula  (dragon-fly),  the  opening  is  simple, 
being  covered  by  two  very  small  oval  valves.  The  seminal 
vesicle  is  placed  in  a  depression  at  the  base  of  the  abdomen. 
Under  sexual  excitement  the  male  fills  the  vesicle  (which, 
owing  to  the  flexibility  of  the  abdomen,  is  readily  accom- 
plished) and  secures  the  female  about  the  neck  by  the  anal 
claspers.  He  remains  passive  during  coition,  which  is  ac- 
complished by  the  female  placing  her  genital  pore  in  con- 
nection with  that  of  the  vesicle. 

Arachnida. — Sexes  distinct,  except  in  Tardigrada.  Ovaries 
or  testicles  double,  blended  together  on  the  median  line; 
they  have  two  excretory  ducts  which  open  by  a  single  pore 
at  the  base  of  abdomen  or  under  the  thorax.  Rarely  is  there 
an  ovipositor  or  penis  as  in  Phalangidse.  Accessory  glandules 
to  the  oviduct  or  vas  deferens  do  not  differ  essentially  from 


116  COMPARATIVE   ANATOMY. 

those  of  insects.  Coition  always  occurs.  Copulatory  organ 
of  male  frequently  complicated.* 

YERTEBRATA.  Pisces.  —  Ovaries  (roe)  generally  double. 
Single  in  many  cartilaginous  fishes,  and  in  Perca  (perch). 
In  Amphioxus,  Anguilla  (eel),  and  Salmo  (salmon),  the  ovaries 
are  without  oviducts.  They  are  either  '  adherent  by  one  side 
to  the  walls  of  the  abdominal  cavity,'  or  engaged  within 
loose  festoons  of  the  peritoneum.  The  eggs  are  discharged 
into  abdominal  cavity,  in  all  probability,  to  escape  by  minute 
pores  placed  one  on  either  side  of  the  median  line  immedi- 
ately behind  the  anus.  In  marsipobranchiate  fishes  and 
Acipenser  (sturgeon)  the  eggs,  after  escape,  are  received 
into  short  incomplete  oviduct.  In  Selachia  the  ovaries  are 
placed  at  the  anterior  portion  of  abdomen,  and  are  distinct 
from  oviduct.  The  latter  is  dilated  at  its  inferior  portion  into 
a  longitudinally  plicated  chamber,  which  is  analogous  to  a 
uterus.  A  somewhat  similar  dilatation  is  met  with  in  Blen- 
nius  vivaparus  and  Anableps. — In  osseous  fishes  the  ovaries, 
which  are  relatively  of  great  size,  are  more  defined,  and  en- 
closed within  a  capsule.  They  communicate  directly  with 
the  oviducts,  so  that  the  eggs  may  be  said  to  be  discharged 
internally,  thereby  differing  from  all  other  vertebrates.  The 
oviducts  may  unite,  as  in  Clupea  (herring),  or  proceed  sep- 
arately to  terminate  at  a  common  genital  pore. 

Between  the  external  form  of  the  testicle  (milt)  and  ova- 
ries of  most  fishes  no  prominent  distinctions  exist.  The 
sperm  cells  are  arranged  within  a  cellular  matrix  and  with- 
out seminal  ducts,  as  in  Amphioxus,  marsipobranchiates,  and 
Pkuronectes  (flounder).  The  cells  line  terminal  ends  of  coiled 
tubes,  which  often  join  the  excretory  duct,  as  in  majority  of 

*  "  Spiders  use  their  hollow,  spoon-shaped  palpi  in  copulation.  These  are 
filled  with  sperm  and  applied  to  the  entrance  of  the  vulva.  For  this  pur- 
pose, the  last  article  of  the  palpi,  which  is  always  hollow  and  much  enlarged, 
contains  a  soft  spiral  body  terminated  by  a  curved,  gutter-like,  horny  pro- 
cess. Besides  this,  there  is  an  arched,  horny  filament,  and  several  hooks, 
and  other  appendages  of  the  most  varied  forms.  These  are  protractile,  and 
serve,  some  to  seize  the  female,  and  others  as  conductors  of  the  sperm." 
(Siebold.) 


REPRODUCTIVE    SYSTEM.  117 

osseous  fishes," — or  they  are  arranged  within  chamber  commu- 
nicating by  convergent  seminal  canal  with  a  single  tortuous 
duct,  which  pursues  a  zigzag  course,  to  widen  at  its  lower 
portion.  It  here  receives  the  duct  of  its  fellow,  to  finally  ter- 
minate at  a  point  just  within  the  cloaca. — Penis  small.  Two 
conspicuous  organs,  composed  of  several  segments  of  carti- 
lage, are  placed  upon  opposite  sides  of  genital  pores.  They 
are  termed  claspers,  and  are  employed  in  coition. 

Batrachia. — The  ovaries  possess  free  opening  into  cavity 
of  abdomen  at  upper  portion  of  abdominal  cavity.  The 
oviduct  tortuous,  and  in  relation  to  the  organ  as  in  man,  is 
often  of  great  length.  In  Eana  (frog)  the  lower  portions  of 
tubes  dilate  into  a  sac  for  temporary  retention  of  eggs,  to 
terminate  in  ureter.  The  testicles  lie  upon  each  side  of 
spinal  column  upon  the  fore  part  of  the  kidneys.  Penis 
none  in  Rana;  rudimentary  in  Proteus. 

Reptilia. — The  ovaries,  situated  in  the  loins,  are  racemose, 
diffuse,  and  distinct  from  oviduct.  The  latter  is,  through- 
out greater  portion  of  length,  thickened  with  numerous 
follicular  glandular  appendages,  and  terminates  in  urethra 
immediately  in  front  of  the  urinary  bladder.  The  testicles  are 
also  in  loins,  and  communicate  with  cloaca  by  a  long  flexuous 
vas  deferens.  Penis  in  Ophidia  and  Sauria  is  divided  along 
its  entire  length.  The  two  separate  cavernous  bodies  imper- 
forate  and  armed  with  spines.  Organ  prehensile  as  well 
as  intromittent.  It  is  penetrated  by  two  canals  that  run 
through  their  long  diameter  from  behind  forwards  to  termin- 
ate blindly  at  the  glans.  In  Chelonia  and  Crocodilia  the 
cavernous  bodies  converge  and  in  part  unite.  There  is  no 
production  of  urethra  in  the  organ,  a  groove  in  median  line 
serving  for  conduction  of  sperm.  Spongy  body  absent. 
Erection  is  secured  by  muscular  action. 

Aves. — The  ovary  of  left  side  is,  as  a  rule,  alone  devel- 
oped. Certain  birds  of  prey  have  both.  Originally  the  or- 
gan is  fiat,  and  marked  with  transverse  folds.  When  dis- 
tended by  eggs  in  various  degrees  of  development  it  assumes 
a  racemose  appearance.  Each  ovum  is  surrounded  by  a 
vascular  ovisac  (calyx),  which,  when  mature,  is  pediculated, 


118  COMPARATIVE   ANATOMY. 

and  disappears  after  expulsion  of  egg.  The  oviduct,  when 
quiescent,  is  straight,  but  when  the  female  is  under  sexual 
excitement,  convoluted.  After  receiving  various  glandular 
appendages  designed  to  secrete  accessories  to  the  eggs,  it 
empties  into  the  cloaca.  Clitoris  well  developed  in  Struthio 
(ostrich). — The  testicles,  two  in  number,  are  placed  at  upper 
extremity  of  kidney.  They  vary  in  color,  a  shade  of  yellow 
being  the  prevailing  hue.  Yas  deferens  generally  slightly 
convoluted,  and  empties  into  cloaca.  Penis  is  an  extra- 
version  of  mucous  membrane  having  erectile  tissue  in  its 
walls,  as  in  Gallus  (cock),  or  very  long,  convoluted,  and 
grooved  along  dorsal  surface,  as  in  the  Natatores. 

Mammalia. — The  ovaries  are  always  two  in  number.  Orni- 
thorhynchus  (duck-bill),  right  small  and  imperfect.  Bodies 
oval,  compressed;  stroma  rather  dense,  fibroid.  In  Impla- 
centalia,  the  oviduct  (Fallopian  tube)  expands  at  lower  por- 
tion (uterus)  in  Monotremata,  and  afterwards  abruptly  con- 
tracts to  open,  in  common  with  the  urethra,  with  the  fellow 
of  opposite  side  in  a  wide  passage  (urogenital  canal),  which 
leads  to  a  second  chamber  yet  in  advance,  the  vestibule. 
The  rectum  joins  the  vestibule  at  its  inferior  portion  to  form 
the  cloaca. — In  Marsupialia  the  oviducts,  as  they  descend, 
enlarge  to  open  by  contracted  papillated  extremities  into  the 
vagina,  which  is  peculiar  in  having  a  central  pendulous 
chamber  resembling  a  uterus  (vaginal  cul-de-sac),  which  may 
be  large,  as  in  Macropus  (kangaroo),  or  small,  as  in  Didelphis 
(opossum).  From  either  side  of  this,  at  its  upper  part,  two 
vaginal  canals  are  given  off,  which,  converging,  empty  into 
the  urogenital  canal  below. 

In  Placentalia  the  two  oviducts  open  into  a  median  mus- 
cular cavity,  the  uterus.  This  is  markedly  prolonged  at  its 
angles  (cornua)  in  majority  of  mammals — slightly  cornuated 
in  Quadrumana  (monkeys),  not  at  all  in  human  female. 
Uterus  opens  into  a  second  canal  (vagina)  which  terminates 
externally,  receiving  near  its  verge  the  urethra.  Clitoris, 
large  in  Quadrumana,  and  sometimes  possesses  a  bone. 
Longitudinal  septum  occasionally  present  in  vagina.  A 
powerful  sphincter  vaginse  present  in  the  bitch. 


REPRODUCTIVE    SYSTEM.  119 

The  testicles  are  always  two  in  number.  In  Monotre- 
mata,  Elephas  (elephant),  Hyrax  (daman),  many  edentates, 
and  among  carnivores,  Lutra,  (otter),  Viverra,  (civet),  Phoca 
(seal),  and  all  cetaceous  animals,  testicles  are  held  in  abdo- 
men most  generally  close  to  the  kidneys.  In  other  mammals 
they  are  situated  in  the  groin  either  concealed  beneath  the 
common  integument  or  contained  within  a  pendulous  sac 
(scrotum),  which  commonly  lies  beneath  the  pubic  bones, 
but  in  Marsupialia  is  lodged  in  the  inguinal  pouch  in  advance 
of  the  penis. — Yas  deferens  if  tortuous,  markedly  plicated. 
Prostate  gland  commonly  present;  absent  in  Rodentia,  with 
whom  Cowper's  glands  are  more  than  usually  developed.  The 
latter  are  of  two  pairs  in  Didelphis  (opossum),  three,  in  Ma- 
cropus  (kangaroo);  large,  and  lie  upon  ischii  in  Erinaceus 
(hedge-hog),  while  in  Herpestis  the  ducts  are  long,  and  empty 
into  urethra  near  its  extremity.  Preputial  glands  are  large 
in  Fiber  zibethicus  (musk  rat),  and  Castor  fiber  (beaver).  Ye- 
siculse  seminales  absent  in  Marsupialia  and  Carnivora,  and 
Cetacea;  present  in  man,  monkey,  bat,  shrew,  hedge-hog, 
and  elephant. — Penis.  Cavernous  bodies,  with  exception  of 
Irnplacentalia,  are  attached  to  ischiatic  bones, — the  spongy 
bodies  surrounding  urethra.  A  bone  often  placed  in  septum 
between  cavernous  bodies;  present  in  some  Quadrumana,  as 
in  Gorilla,  and  in  Carnivora,  as  in  Ursus  (bear).  The  cavern- 
ous bodies  in  Macropus  (kangaroo)  enclose  the  spongy  body, 
the  latter  is  also  bifid  at  base  and  cleft  at  apex.  This  is 
either  acuminate,  as  in  Ruminantia, — and  Phoccena  (porpoise), 
or  capitate.  It  is  provided  with  spine-like  processes  in  many 
Felidse  and  Cava  (guinea-pig);  while  it  is  large,  irregularly 
cylindroid,  with  thickened  base  in  Canis  (dog). 


120  COMPARATIVE   ANATOMY. 

XVI. 

GENERATION, 

GENERATION  is  the  production  of  offspring. 

Six  methods  apparent.  The  first  is  true  generation, 
the  remaining  five  (agamic)  may  be  considered  its  acces- 
sories. 

(1)  That  of  the  egg. — This,  so  far  as  is  known,  is  constant 
among  animals,  hence  the  aphorism  "  Omne  vivum  ex  ovo." 
(Harvey.) 

(2)  Conjugation. — This  is  the  result  of  union  of  two  or- 
ganisms apparently  without  intervention  of  sexual  apparatus, 
as  in  Gregarinse. 

(3)  Encapsulation. — This  is  the  formation  of  a  capsule 
within  the  parent  tending  to  engross  the  area  of  the  entire 
animal,  from  the  changes  within  which  a  new  being  arises, 
as  in  Infusoria. 

(4)  Fissuration. — This  is  spontaneous  division  of  parent; 
each  half  assuming  the  shape  and  properties  of  the  original 
form,  as  in  Infusoria. 

(5)  Gemmation. — This  is  the  formation  of  buds  (gemmae), 
which  after  acquiring  the  characters  of  the  stock  from  which 
they  spring,  may  retain  their  connection  with  the  parent,  as 
in  hydra  buds  of  Eucope,  or  become  detached — free  gemmae, 
as  in  Hydra.    Buds  may  arise  beneath  the  integument — the 
common  way — or  originate  from  the  interior,  forming  curious 
ova-like  masses,  as  in  Aphis  and  Ceddomyia. 

(6)  Alternate  Generation  (larval  generation,  asexual  gen- 
eration, virgin  generation,  parthenogenesis,  polymorphism, 
metagenesis). — When  from  a  freed  gemma  one  or  more  dis- 
similar  forms   arise,    and  when   from   these — constituting 
broods  of  sexless  beings — other  unlike  forms  issue, — either 
through  repetition  of  the  process  of  gemmation,  as  in  Coryne, 
or  by  fissuration,  as  in  Aurelia,^-&Yid  when  within  these  be- 
ings, in  turn,  sexual  organs  are  developed,  and  propagation 


GENERATION.  121 

occurs  through  ova, — the  animal  is  said  to  produce  by  alter- 
nate generation.* 

The  changes  which  take  place  in  the  impregnated  egg  in 
the  evolution  of  the  embryo  are  said  to  be  due  to  the  pres- 
ence of  a  peculiar  force,  recognized  as  the  germ  force. f 

Since  this  is  equally  pronounced  in  all  ova,  and  the  tissues 
of  the  embryo  in  each  case  are  obtained  at  its  expense,  it 
follows  that  in  comparatively  simple  animals  a  large  surplus 
of  power  is  held  over  and  above  that  actually  employed  in  the 
maintenance  of  the  adult  form,  and  which  is  capable  of  being 
expressed  by  jlssuration  or  gemmation  in  new  organisms  resem- 
bling the  parent.  But  when  the  force  is  in  a  measure  ex- 
hausted by  the  evolution  of  a  complex  organization,  repetition 
of  the  form  of  the  animal  can  be  effected  only  by  the  develop- 
ment consequent  upon  the  union  of  new  sexual  elements.  It 
may,  therefore,  be  stated  in  general  terms,  that  the  amount  of 
germ  force  present  in  a  mature  organism  is  in  inverse  ratio 
to  the  extent  to  which  tissues  have  been  developed,  or,  in 
other  words,  to  the  degree  to  which  functional  labor  has 
been  divided. — In  Infusoria,  where  this  specialization  is 

*  This  term  was  introduced  by  the  discoverer  of  the  method,  Steenstrup, 
who  entertained  the  opinion  that  the  first  brood  of  larvae  retained  the  power 
of  producing  young,  without  themselves  possessing  sexual  organs.  The 
following  is  his  original  definition:  "Alternate  generation  is  the  phenomenon 
of  an  animal  producing  an  offspring  which  at  no  time  resembles  the  parent, 
but  which  on  the  other  hand,  itself  brings  forth  a  progeny  which  returns  in 
its  form  and  nature  to  the  parent  animal,  so  that  the  maternal  animal  does 
not  meet  with  its  resemblance  in  its  own  brood,  but  in  its  descendants  of  the 
second,  third,  and  fourth  degrees  of  generation." 

The  author  would  consider  the  phenomena  of  alternate  generation  as  true 
larval  changes,  differing  in  degree  only  from  those  of  more  direct  develop- 
ment, and  producing,  as  the  result  of  a  single  impregnation,  not  one,  but  it 
may  be,  many  sexual  forms. 

f  "Of  this  force,  by  whatever  name  we  designate  it,  whether  as  the  forma- 
tive or  the  plastic,  or,  more  explicitly,  as  the  force  by  which  organic  matter, 
in  appropriate  conditions,  is  shaped  and  arranged  into  organic  structures ; 
of  this  force,  and  of  those  that  co-operate  with  it,  we  can,  I  think,  only  ap- 
prehend that  they  are  in  the  completed  organism,  the  same  with  those  which 
actuated  the  formation  of  the  original  tissues  in  the  development  of  the 
germ  and  of  the  embryo."  (Paget.) 


122  COMPARATIVE   ANATOMY. 

small,  fissuration  and  gemmation  occur;  but  neither  are 
seen  in  Vertebrata,  where  the  specialization  is  great. 

The  application  of  these  facts  to  a  proper  appreciation  of 
the  process  of  repair  is  extensive.  It  will  be  seen  that  when 
the  reserved  farce  is  large  that  losses  sustained  by  mutilation 
— which  may  be  carried  to  an  indefinite  extent — are  at  once 
recovered  by  the  evolution  of  new  individuals  from  the  severed 
portions ;  as  is  seen  in  Infusoria,  Hydra,  Actinia,  and  in  a  less 
degree  in  Lumbricus  (earthworm).  When  the  force  is  smaller, 
limited  portions  only  of  an  individual  can  be  restored  after 
such  injury.  Thus  the  viscera  of  Holothuria  (sea-cucumber), 
limbs'  of  Ophiura  and  Lupa  (crab),  head  of  Helix  (snail),  eye 
and  limb  of  Proteus  (salamander),  fin  offish  and  tail  of  lizard, 
are  the  only  portions  capable  of  being  reproduced ;  for  death 
may  ensue  if  the  injury  prove  extensive.  In  Aves  and  Mam- 
malia, so  perfect  is  the  specialization  of  function  that  the 
power  named  operates  but  feebly;  instances  of  its  sustained 
activity  are  rare.* 

PROTOZOA.  Rhizopoda. — Generation  imperfectly  known. 
Forarninifera  increase  in  size  by  gemmation.  Ova-like 
bodies  have  been  detected  in  the  same  group.  (Wallich.) 

Infusoria. — Generally  propagate  by  fissuration  and  gem- 
mation. Fissuration  frequently  occurs — longitudinally,  as  in 
Vorticella,  transversely  with  others,  as  in  Stentor,  and  in  others 
again  by  both  methods,  as  in  Paramecium. — Gemmation  is 
more  rare,  as  in  Vorticella.  The  'nucleus'  is  always  present  in 
Infusoria.  It  may  be  single,  as  in  Paramecium,  or  multiple,  as 
in  Stylonychia.  It  is  always  divided  in  the  act  of  fissuration. — 
In  Vorticella,  in  addition  to  the  above  methods,  encapsulation 
occurs.  The  animal  about  to  undergo  this  process  loses  its 
identity  by  becoming,  for  the  most  part,  converted  into  a  cap- 
sule having  thickened  walls.  The  nucleus  assumes  a  band-like 
form,  which  after  a  time  divides  into  a  number  of  disciform 
bodies,  giving  the  capsule  a  sacculated  appearance.  Within 

*  These  truths  remind  us  that  it  is  an  error  to  endeavor  to  explain  too 
exactly  the  morbid  processes  going  on  in  man  by  what  is  observed  in  appa- 
rently similar  conditions  among  lower  animals. 


GENERATION.  123 

this,  numerous  motile  larvse  are  developed,  which  after  a  time 
escape  by  rupture  of  the  wall  of  the  cyst,  subsequently  to 
assume  the  form  of  the  parent,  most  probably  without  meta- 
morphosis. Occasionally  from  the  sacculated  stage  an  acineti- 
form  larva  (so  called  from  its  general  resemblance  to  the 
genus  Acinetd)  arises,  from  the  interior  mass  of  which  Vorti- 
cellce  successively  escape.*  In  Paramecium  true  generation 
may  occur  following  coition.  Entire  segmentation  of  the 
ovum  occurs,  and  the  young  almost  directly  assume  the 
form  of  the  parent. — In  Trichodes  an  encapsulated  stage  ap- 
parently intervenes  between  the  first  larval  and  mature  con- 
dition. 

EADIATA.  Coelenterata. — Eeproduction  in  Polypi  by  fis- 
suration,  gemmation,  and  true  generation.  In  addition  to 
remarkable  capacity  to  multiply  by  fissuration  and  gemma- 
tion, the  Hydra  periodically  produces  young  by  true  gener- 
ation. It  may  be  hermaphroditic  or  unisexual,  but  more 
commonly  the  former.  The  development  is  without  meta- 
morphosis. In  Actinia  (sea-anemone),  which  is  hermaphro- 
ditic, the  egg  is  impregnated  in  the  water.  After  complete 
segmentation  it  becomes  ciliated.  The  embryo  in  time  as- 
sumes a  horseshoe  form,  the  outer  boundary  of  which  event- 
ually constitutes  the  periphery  of  the  animal,  the  inner 
boundary,  the  common  visceral  cavity. 

In  Acalephse  are  witnessed  some  of  the  most  remarkable 
methods  of  development  known  in  the  animal  kingdom. 
They  are  for  the  most  part  examples  of  alternate  generation. 
In  Hydroida  this  process  is  particularly  complicated.  The 
following  terms  will  be  employed  in  its  description : 

Planula.     The  freed  embryo. 

*  Encapsulation  resembles  true  generation  in  the  following  particulars : 
1st.  The  'nucleus'  contained  within  the  capsule  is  analogous  to  an  ovum. 
During  encapsulation  this  undergoes  segmentation,  producing  numbers  of 
distinct  larval  forms. 

2d.  The  presence  of  male  and  female  organs  within  the  capsule  being 
assumed,  animals  undergoing  encapsulation  are  hermaphroditic, — a  conclu- 
sion in  harmony  with  facts  observed  in  closely  allied  animals,  the  Spongida, 
as  in  Tethya. 


124  COMPARATIVE   ANATOMY. 

Hydroid  stock  (stolon).  Its  second  stage  of  development. 
It  may  be  free,  as  in  Nanorwa,  or  fixed,  as  in  Eucope. 

Hydra.  A  sexual  bud  (so  called  from  its  resemblance  to 
the  genus  Hydra)  attached  to  the  hydroid  stock. 

Medusa  bud  (special  gemma).  A  bud  springing  from 
the  hydroid  stock,  possessing  the  form  of  the  Medusae.*  It 
may  be  permanently  asexual,  as  in  Nanomia,  or  possess 
power  of  developing  into  sexual  form,  as  in  Eucope.  It  may 
remain  attached  to  hydroid,  as  in  Nanomia,  or  become 
detached,  as  in  Eucope.  Occasionally  successive  medusa 
buds  arise  from  it  by  gemmation,  as  in  Coryne. 

Calyx.  A  capsule  developed  in  the  axils  of  the  branched 
hydroid  stock,  having  for  contents  medusa  buds,  as  in  Cam- 
panularia,  or  male  or  female  organs,  as  in  Cordylophora. 

Hydroids  pass  the  earlier  stages  of  their  existence  as 
little  shrub-like  communities,  as  in  Eucope,  or  remain  in 
that  condition  through  life,  as  in  Cordylophora.  Hydrse 
are  transformed  into  jelly-fishes,  which,  in  some  instances, 
break  off  when  mature,  and  swim  away  as  free  animals,  as 
in  Eucope,  while  in  others,  as  in  Laomedea,  they  remain  per- 
manent members  of  the  hydroid  stock,  never  assuming  a 
free  mode  of  life.  All  these  buds,  when  mature,  whether 
free  or  fixed,  lay  eggs  in  their  turn,  from  which  a  fresh  stock 
arises  to  renew  the  singular  cycle.  (E.  C.  &  A.  Agassiz.) 

In  Nanomia  the  planula  is  of  an  elliptical  shape  without 
cilia,  and  contains  an  oval  chamber  filled  with  an  oily  fluid 
which  buoys  the  embryo.  The  planula  develops  directly  into 
a  short  hydroid  stock,  the  oil  chamber  being  retained.  Three 
kinds  of  hydrse  are  evolved  from  the  stock,  as  follows:  (1)  An 
open  proboscidiform  bud,  with  numerous  long  and  delicate 
tentacles  springing  from  its  base,  each  knobbed  at  the  end 
and  paved  with  lasso  cells.  (2)  Similar  to  the  preceding  ex- 
cepting tentacles  are  short  and  twisted.  (3)  A  closed  hydra 
with  a  single  pendent  tentacle  of  moderate  length.  The  first 
two  forms  are  held  to  be  feeders  to  the  stock;  the  function 

*  'Medusa,'  a  genus  of  Discophora,  is  here  employed  in  the  plural  to 
include  a  variety  of  medusiform  zooids. 


GENERATION.  125 

of  the  last  is  unknown. — Two  kinds  of  medusa  buds  also 
spring  from  the  stock.  The  first  of  these  (swimming  bells) 
are  asexual.  They  remain  attached  to  and  move  the  stock 
by  the  contractility  of  their  walls.  In  the  second  kind,  more 
numerous  than  the  preceding,  the  bells  are  of  smaller  size, 
remain  attached  to  stock,  and  at  breeding  seasons  develop 
sexual  organs.  Male  and  female  elements  contained  in  sep- 
arate capsules.  The  impregnated  egg  gives  birth  to  planulee 
as  before. 

In  Cordylophora  the  planula  is  ciliated  and  of  an  oval  form. 
It  soon  becomes  fixed,  and  develops  through  the  winter  a 
fixed  hydroid  stock.  From  this  numerous  hydrse  arise  by 
gemmation,  each  consisting  of  an  elongated  conoidal  form 
surmounted  by  tentacles.  The  following  spring,  two  forms 
of  calyces  are  seen,  one  for  the  development  of  ova,  the  other 
for  spermatozoa.  Impregnation  occurring  after  a  method 
imperfectly  understood,  the  contents  of  the  ovisac  undergo 
segmentation,  and  a  number  of  planulse  escape,  each  of  these 
in  turn  to  become  fixed  and  develop  the  stock  as  before. 
(Allman.) 

Ehizogeton  resembles  Cordylophora  in  having  hydrse  and 
male  and  female  calyces  developed  from  hydroid  stock.  But 
is  peculiar  in  the  stock  not  being  shrub-like,  but  trailing; — 
each  hydra  and  generative  capsule  (calyx)  arises  by  its  own 
trunk.  It  appears  probable  that  the  calyces  may  be  pro- 
duced from  hydree.  The  method  of  development  of  ova  is 
not  known.  (Clark.) 

In  Eucope  the  form  of  the  planulse  and  the  stock  are  the 
same  as  in  Cordylophora.  But  when  the  special  gemmse  are 
developed,  but  one  form  of  calyx  is  seen,  namely:  that  for 
the  development  of  the  Medusae.  Each  capsule  contains 
about  twenty  to  thirty  buds,  which,  becoming  detached,  es- 
cape and  develop  organs  of  generation,  to  bring  forth  in 
their  turn  planulse. 

In  Perigonimus  no  calyces  are  seen,  the  medusa  buds  spring- 
ing directly  from  the  sides  of  the  stock,  subsequently  to 
become  detached. 

In  Tubularia  the  hydraa  are  covered  in  by  an  extension  of 


126  COMPARATIVE   ANATOMY. 

the  sheath  of  the  stock.  The  medusa  buds  arise  without  true 
calyces,  and  assume  the  form  of  the  genus  fierce,  causing  this 
form  to  resemble  the  ctenophorous  ccelenteratates,  as  those 
having  true  medusa  buds  resemble  the  discophorous.  At 
other  times  in -the  same  genus  a  hydraform  bud  escapes  from 
a  simple  calyx.  It  is  not  known  which  of  these  special  gem- 
mse  produce  the  organs  of  generation. 

In  Coryne,  Hydra  is  a  club-shape  appendage  to  stock  or 
the  medusa  bud  (Sarsia),  develops  eggs,  as  in  Mteope,  is  asex- 
ual, and  develops  other  medusa  buds  from  its  proboscis,  its 
ovaries,  or  from  the  base  of  its  tentacles  (see  Salpa,  p.  128). 
These  remain  attached  for  some  time,  but  becoming  sepa- 
rated, develop  organs  of  generation  to  bring  forth  planulse. 

In  Hybocodon  the  medusa  bud  is  developed  directly  from 
the  stock  without  calyx.  It  is  peculiar  in  being  asexual  and 
in  possessing  but  one  fully-developed  tentacle.  From  the 
base  of  this  from  ten  to  twelve  other  medusa  buds  arise  to 
remain  attached.  At  this  period  the  asexual  bud  becomes 
free  and  swims  off  with  its  burden  of  special  gemmae,  each 
of  which  evolves  sexual  organs  to  bring  forth  planulse.  (E.  C. 
&  A.  Agassiz.) 

In  Dicoryne  male  and  female  medusa  buds  arise  from  cap- 
sules. They  are  of  oblong  form,  but  in  place  of  disk  present 
two  ciliated  tentacles.  (Allman.) 

The  Discophoree,  with  some  few  exceptions,  as  in  Campa- 
nella,  in  which  they  develop,  like  the  Ctenophorse,  from  eggs, 
begin  life  as  Hydra-like  animals,  the  subsequent  self-division 
of  which  gives  rise,  by  a  singular  process,  to  a  number  of 
distinct  jelly-fishes.  (E.  C.  &  A.  Agassiz.) 

In  Amelia,  the  impregnated  egg  is  conveyed  to  a  marginal 
pouch  from  the  ovarian  chamber  after  a  manner  unknown. 
It  here  develops  into  a  hydraform  larva  (strobila,  Scyphos-' 
toma\  which  subsequently  undergoes  transverse  fissuration, 
each  segment  (Ephyrd)  assuming,  during  the  process  of  divi- 
sion, the  form  of  the  parent,  afterward  to  develop  sexual 
organs  and  produce  strobilse  as  before. 

Ctenophorse  grow  from  eggs  by  a  direct,  continuous  pro- 
cess of  development,  without  undergoing  any  striking  meta- 
morphosis. (E.  C.  &  A.  Agassiz.) 


GENERATION.  127 

Echinodermata. — The  first  condition  of  every  Echinoderm 
is  the  same, — an  oval,  ciliated  body,  resembling  an  infusorial 
animalcule,  and  without  external  organs  or  distinction  of 
parts.  Upon  this  form  are  developed,  at  one  part,  peduncles 
for  its  attachment  to  other  bodies,  while  the  rest  of  the  germ 
increases  in  size  and  assumes  a  star-fish  form.  The  larvae 
may  be  divided  into  two  groups: 

(1)  The  first — including  the  Ophiuridae  and  Echinidae — are 
somewhat  hemispherical  bodies,  with  one  edge  of  their  trun- 
cated side  prolonged  into  a  single  flat  and  wide  process,  which 
carries  the  mouth  and  oesophagus;   while  from  the  oppo- 
site extremity  project  rods,  four,  eight,  or  more  in  number, 
which   form   the   internal   skeleton.     These    larvae   have   a 
globular  stomach  in  their  hemispherical  portion,  from  which 
proceeds  a  short  intestine,  terminating  in  a  circular  anus. 
They  have,  moreover,  a  ciliated  fringe,  which  consists  of  a 
ridge  covered  with  large  cilia,  passing  around  the  mouth  and 
before  the  arms,  completely  encircling  the  body  in  an  oblique 
manner.    The  larval  form  of  the  Echinidae  is  often  spoken  of 
as  the  Pluteus. 

(2)  The  second  group — including  the   Holothuridae  and 
Asteroidae — differs  from  the  above  in  not  possessing  an  in- 
ternal skeleton.    The  larvae  of  the  Holothuridae  are  concavo- 
convex   bean-shaped   bodies,   with   an   irregular  transverse 
fissure  answering  to  the  hilum  of  the  bean,  in  which  the 
mouth  is  placed.     The  margins  of  this  fissure  are  ciliated; 
the  anus  opens  on  the  ventral  surface.     Those  of  the  Aste- 
roidse  closely  resemble  these  last,  but  they  have  a  distinct 
ciliated  circle  in  front  of  the  mouth ;  as  they  increase  in  size, 
the  anterior  part  of  their  body  is  covered  with  long  processes, 
which  vary  according  to  different  forms.     The  names  Auri- 
cularia  and  Bipinnaria  are  often  applied  to  these  larvae  respec- 
tively. (Burnett.)     Brachiolaria  is  the  larva  of  Asteracanthion. 

MOLLUSCA.  Polyzoa. — In  addition  to  a  direct  egg-develop- 
ment, the  Polyzoa  multiply  by  gemmation. 

Tunicata. — Reproduction  by  budding  sometimes  occurs,  as 
in  the  compound  Ascidians;  but  true  generation  is  more 
frequently  recognized.  After  complete  segmentation  an  ob- 


128  COMPARATIVE   ANATOMY. 

long,  tailed  embryo*  is  developed,  which  escaping  from  egg 
moves  freely  in  the  water.  After  a  few  hours  it  becomes 
fixed,  loses  its  caudal  appendage,  and  without  further  change 
is  developed  into  the  sexual  form. 

The  phenomena  of  alternate  generation  are  witnessed  in 
Salpa.  The  egg  undergoing  complete  segmentation  evolves 
a  larva  which  assumes  a  form  recalling  that  of  the  parent,  to 
which  it  remains  for  some  time  attached  by  a  placenta-like 
structure.  Kupturing  the  connection,  a  curious  process  of 
gemmation,  which  was  commenced  while  the  larva  was  yet 
confined,  is  completed.  This  consists  in  the  formation  from 
a  central  cylindroid  stem  (stolon)  of  numbers  of  buds,  all  of 
which  being  evolved  at  about  the  same  time 4  adhere  together 
by  their  external  surfaces  or  special  organs  of  attachment' 
forming  chains  or  clusters  of  sexual  individuals.  These  are 
generally  composed  of  two  rows  joined  together  by  several 
cords  and  enveloped  in  a  common  membranous  tube.  The 
sexual  form  is  known  as  the  ' aggregated  Salpce'  or  ' stock,' 
the  larval  or  non-sexual,  as  the  i  solitary  Salpa.9 

In  Pyrosoma,  the  yolk  is  diffused  within  ovisac  at  an  early 
stage  of  development,  and  while  the  embryonal  mass  is  yet 
newly  formed,  it  partially  segments  transversely  into  five 
divisions.  The  first  of  these  is  a  provisional  structure;  the 
other  four  are  permanent  ones,  and  each  subsequently  at- 
tains the  sexual  form.  While  within  the  parent  they  are 
joined  together  by  a  connecting  band.  The  subsequent 
growth  of  each  of  the  embryos  into  a  compound  animal  has 
not  been  traced. 

Brachiopoda. — Development  but  little  known.  In  Crania 
the  young  possesses  four  pairs  of  ciliated  processes,  situated 
around  the  mouth,  and  which,  together  with  the  gullet,  can 
be  protruded  from  the  cavity  of  the  shell.  It  bears  a  strong 
resemblance  to  the  permanent  condition  of  Polyzoa. 

Lamellibranchiata. — Egg  not  uncommonly  possesses  a  mi- 

*  To  avoid  multiplication  of  terms  'embryonal'  and  'larval  forms'  will 
be  used  indifferently,  though  in  so  doing  a  lack  of  precision  is  acknowl- 
edged. 


GENERATION.  129 

cropyle,*  as  in  Anodonta  (mussel).  Segmentation  partial. 
Superficial  layer  not  participating  in  the  process.  The  cili- 
ated and  revolving  embryo  divides,  and  is  crowned  with  a 
valvular  appendage  developed  from  the  unsegmented  super- 
ficies. The  embryo  divides  into  halves,  each  half  being  cov- 
ered by  a  valve.  In  the  middle  of  the  angle  formed  by  these 
valves  is  raised  a  short  hollow  cylinder — the  byssus-forming 
organ — and  out  of  which  projects  a  long  transparent  byssus. 
(Siebold.) 

Gasteropoda. — Segmentation  of  vitellus  complete,  except- 
ing a  few  hyaline  corpuscles.  Embryo  oblong,  indented,  and 
ciliated  at  one  extremity.  The  indentation  deepens  in  Eolis 
and  Doris,  forming  two  lobules  upon  whose  borders  very  long 
cilia  are  developed.  The  crests  are  absent  in  certain  pul- 
monates.  A  third  eminence  is  developed  between  these  two 
pinions,  and  ultimately  changed  into  a  foot.  A  spiral  shell 
and  operculum  are  very  constantly  present,  whether  the  ma- 
ture form  be  conchiferous  or  not.  Subsequently  the  pinions 
disappear,  and  in  the  naked  species  the  shell  and  operculum 
are  lost.  From  an  early  time  in  development  the  embryo  ro- 
tates upon  its  axis  by  alternate  revolutions.  In  naked  pul- 
monates  a  sac  analogous  to  umbilical  vesicle  is  formed  at 
caudal  region  of  embryo,  which,  during  development,  altern- 
ately contracts  with  embryo. 

Cephalopoda. — Segmentation  partial.  In  the  germinative 
area  upon  the  upper  portion  of  the  egg  a  two-layered  blasto- 
dermic  membrane  originates,  from  the  central  and  outer 
portion  of  which  a  disciform  embryo  arises.  Various  irreg- 
ularities mark  its  surface.  An  irregular  median  fold  repre- 
sents the  mantle  enclosing  the  future  visceral  cavity.  Upon 
either  side  of  it  are  seen  the  gills,  the  halves  of  the  funnel, 
cephalic  lobes,  and  the  rudimentary  arms  and  eyes.  The 
mouth  is  not  situated  between  these  organs,  but  at  the  pos- 


*  The  micropyle  is  the  remains  of  the  pedicle  which,  in  the  development 
of  egg,  connects  it  with  the  ovary.  It  is  believed  to  be  the  point  at  which 
entrance  is  effected  by  the  spermatic  filament,  and  is  closed  prior  to  act  of 
conception. 

9 


130  COMPARATIVE   ANATOMY. 

terior  or  dorsal  surface.  A  portion  of  the  vitellus  becomes 
surrounded  by  the  large  median  layer  of  tissue.  The  re- 
maining unappropriated  area  is  defined  externally  by  a  mem- 
brane derived  from  the  inner  layer  of  the  blastodermic  mem- 
brane, and  communicates  with  the  oesophagus  through  a 
narrow  canal.  It  resembles  in  form  the  umbilical  vesicle  of 
vertebrates,  from  which,  however,  it  markedly  differs  in  ab- 
sence of  connection  with  the  abdomen.  The  embryo  is  more 
fully  developed  before  it  is  made  independent  of  its  capsule 
than  is  the  case  in  other  Invertebrata. 

ARTICULATA.  The  following  changes  are  observed  subse- 
quent to  impregnation  in  the  egg  of  an  articulate  animal. 
After  segmentation,  which  may  be  either  complete  or  par- 
tial, a  clear  albuminoid  space  (germinative  area)  is  found 
toward  the  ventral  surface  of  egg,  and  the  yolk,  or  vitelline 
area,  upon  the  dorsal.  The  first  trace  of  organization  is  seen 
in  the  formation  of  the  germinal  layer  (blastodermic  mem- 
brane), which  in  time  surrounds  the  yolk, — its  thickened 
portion  of  the  area  within  the  germinative  area  being  called 
the  germinal  disk.  This  layer  divides  into  two ;  the  outer  (ani- 
mal, serous  or  nervous)  layer  is  devoted  to  the  development 
of  the  skeleton  and  nervous  system, — the  inner  (vegetative, 
mucous  or  subsidiary)  layer  is  given  to  the  evolution  of  the 
organs  of  nutrition.  This  disk  soon  becomes  transversely 
wrinkled,  indicating  the  points  of  formation  of  the  future  seg- 
ments. From  the  ventral  sides  of  the  disk  two  folds  descend 
to  form  a  groove,  within  which  is  developed  the  ganglionic 
chain  of  nerves. 

Entozoa. — See  p.  161. 

Annelida. — Segmentation  complete.  Eggs  spherical  and 
ciliated.  Two  types  with  Hirudinei.  After  the  vitellus  has 
divided  into  many  large  cells,  a  central  one  becomes  distin- 
guished from  the  others  by  its  still  further  division.  This 
becomes  the  digestive  tube.  The  others,  still  dividing,  form 
a  primitive  embryonic  part,  in  which  appear  the  future  ven- 
tral and  nervous  portions.  With  the  Branchiata  there  is  a 
complete  metamorphosis.  The  segmentation  of  the  vitellus 
is  uniform  throughout,  and  this  last  is  finally  changed  into  a 


GENERATION.  131 

round  embryo.  The  embryo  lengthens,  and  the  epithelium 
disappears,  except  in  the  belt-like  parts  of  the  two  extremi- 
ties. (Siebold.) 

In  Autolytus,  the  egg  undergoing  segmentation  produces  a 
sexless  larva  (parent  stock)  which  resembles  the  female  in 
general  outline.  Successive  pairs  of  males  and  females  are 
developed  from  the  posterior  extremity  of  the  parent  stock; 
the  exact  number  has  not  been  ascertained.  (A.  Agassiz.) 

Crustacea. — Embryos  are  often  dissimilar  from  the  adult 
form.  The  most  conspicuous  of  these  is  the  larva  (Zoe)  of 
the  Decapoda,  and  the  active  zoeform  young  of  Cirripedia 
(barnacles)  and  Lernreacea  (lerneans).  The  latter  groups  are 
inclusive  of  animals  with  sexual  forms  so  degraded  that  their 
position  among  articulates  can  be  determined  only  by  observ- 
ing their  larval  conditions. 

Myriapoda. — The  larval  form  differs  from  the  adult  chiefly 
in  possessing  a  smaller  number  of  segments. 

Arachnida. — The  young  of  certain  Acarina  (ticks)  have 
but  six  legs,  as  in  Trombidium. 

Insecta.  —  The  metamorphoses  of  insects  are  various, 
though  fixed  within  natural  groups.  Some,  however,  are 
without  proper  metamorphosis,  as  in  Pediculics  (louse),  and 
Lepisnia  (silver-moth). 

Metamorphosis  is  incomplete  when  the  larval  condition 
closely  resembles  the  parent,  as  in  Hemiptera  (bug)  and 
Orthoptera  (locust).  It  is  complete  when  the  embryo  passes 
through  two  distinct  stages  prior  to  assuming  the  sexual  form. 
The  first  of  these  is  the  larva  proper  (caterpillar) ;  the  second, 
the  pupa  (chrysalis).  The  sexual,  commonly  winged  form,  is 
the  imago.  Examples  are  seen  in  Diptera  (fly),  Lepidoptera 
(butterfly),  Hymenoptera  (bee),  Neuroptera  (dragonfly),  and 
Coleoptera  (beetle).  The  time  required  for  the  completion 
of  these  life-phases  is  subject  to  variation.  Thus  in  Musca 
vomitoria  (meat-fly)  the  entire  development  is  completed 
within  thirty-one  days,  while  in  Cicada  septendecim  (seven- 
teen-year locust)  seventeen  years  are  required.  The  quantity 
and  quality  of  food  consumed  exercises  great  influence  upon 
the  embryo — hastening  or  retarding  development  as  it  is 


132  COMPARATIVE   ANATOMY. 

present  in  sufficient  or  insufficient  quantities,  as  in   Apis 
(bee). 

In  the  Aphides  (plant-lice)  an  example  of  alternate  gene- 
ration is  exhibited.  The  egg,  which  is  laid  by  the  parent  in 
the  fall,  develops  the  following  spring,  at  which  time  it  un- 
dergoes segmentation,  the  resultant  larva  resembling  the 
parent  in  being  active  and  provided  with  limbs.  It  markedly 
differs,  however,  from  apparently  similar  forms  of  other  in- 
sects in  its  power  of  giving  birth,  through  a  phase  of  the 
process  of  gemmation,  to  a  progeny  like  itself.  Ova-like 
buds  are  formed  in  the  neighborhood  of  the  ovaries,  which 
subsequently  assume  the  outline  of  the  parent  insect.  Such 
individuals — eight  in  number — are  free,  active,  and  each  in 
its  turn  brings  forth  eight  others  like  itself.  This  process 
is  successively  repeated  within  each  active  gemma  as  long  as 
the  surrounding  conditions,  which  are  generally  maintained 
to  the  eighth  or  ninth  generation,  are  favorable.  In  the  last 
brood,  brought  forth  toward  the  close  of  the  summer,  the 
sexes  are  for  the  first  time  distinct,  and  the  males  provided 
with  wings.  From  each  of  these  forms  ova  are  produced 
which,  after  lying  inactive  during  the  winter,  undergo  de- 
velopment in  the  following  spring  as  before.  It  has  been 
estimated  that  in  five  generations  of  offspring  a  single  Aphis 
may  be  the  progenitor  of  5,904,1)00,000  descendants. 

In  Cecidomyia  (Hessian-fly) — a  genus  of  dipterous  insects — 
the  mature  female  deposits  ova,  each  having  a  smooth  shell 
and  furnished  with  a  micropyle,  beneath  the  bark  of  dead 
ash-trees.  They  here  soon  develop  into  larvae,  having  no 
peculiar  external  characters,  but  possessing  in  the  posterior 
portion  of  their  visceral  cavity  (in  immediate  relation  to,  and 
perhaps  having  their  origin  within  a  fatty  tissue),  two  ovary- 
like  bodies,  one  on  either  side.  Within  these  are  developed 
spherical  masses  which,  from  their  resemblance  to  eggs,  are 
known  as  pseudova.  Each  pseudovum  evolves  another  larval 
form,  so  that  in  time  there  exists  within  the  tissues  of  the 
primary  larva  as  many  secondary  larvse  as  there  were  origin- 
ally pseudova  developed.  The  parent  larva,  after  changing 
its  exterior  into  a  pupa-like  case,  dies.  The  brood  remaining 


GENERATION.  133 

within  the  case  throughout  the  winter,  escapes  the  following 
spring,  to  undergo  the  usual  metamorphic  change  common 
to  dipterous  insects. 

VERTEBRATA.  Within  the  germinative  area,  which  is 
placed  toward  the  dorsal  surface  of  the  egg,  the  germinal 
membrane  (blastodermic  membrane)  is  formed,  soon  to 
divide  into  an  external  and  an  internal  layer.  The  former, 
in  which  are  subsequently  found  the  organs  of  animal  life, 
namely,  the  nervous  system,  the  muscles,  the  skeleton,  etc., 
has  received  the  name  of  the  serous,  animal  or  nervous  layer. 
The  latter,  which  gives  origin  to  the  organs  of  vegetative  life, 
and  especially  the  intestines,  is  called  the  mucous  or  vegeta- 
tive layer.  By  subdivision  of  the  inner  layer,  a  third  or  in- 
termediate layer  is  formed,  in  which  is  developed  the  circu- 
latory system. — The  first  important  subsequent  change  is 
observed  in  the  external  layer,  where  within  a  translucent 
space,  a  longitudinal  (primitive)  groove  is  formed,  upon  each 
side  of  which  a  fold  (dorsal  lamina,  dorsal  plate)  arises. 
Such  folds  being  converged  join  at  the  median  line  to  con- 
vert the  groove  into  a  canal  (neural  canal)  subsequently  to 
contain  the  cerebro-spinal  axis.  Immediately  beneath  the 
spinal  groove,  indeed  formed  within  its  lower  wall,  a  peculiar 
cartilaginous  body,  the  <  chorda  dorsalis,'  is  seen.  The  verte- 
bral column  is  commonly  developed  within  the  sheath  of  this 
structure,  which,  as  a  rule,  soon  thereafter  disappears.  While 
these  changes  are  being  effected  the  animal  layer  also  extends 
laterally,  partially,  or  entirely  to  enclose  the  yolk  cavity. 

Two  types  of  development:  (1)  aquatic,  and  (2)  terrestrial. 

(1)  Pisces — In  cartilaginous  fishes  an  osseous  vertebral 
canal  never  appears.  With  such  the  chorda  dorsalis  is  per- 
sistent. When  an  osseous  fish  is  just  escaped  from  the  egg, 
the  remains  of  the  vitelline  sac,  now  called  the  umbilical 
vesicle,  are  not  yet  absorbed,  and  often  of  large  size;  the  gill 
covers  are  not  completely  formed;  the  fins  are  without  rays, 
the  mouth,  which  is  placed  transversely,  is  without  teeth. 
External  or  false  gills  are  occasionally  appended  to  the  sides 
of  the  head,  as  in  Carckarias  (white  shark). 

Batrachia. — The  general  resemblance  in  development  to 


134  COMPARATIVE   ANATOMY. 

that  of  the  preceding  class  marked.  A  distinct  metamor- 
phosis seen  in  young  of  Eana  (tadpole).  The  features  of  this 
stage,  viz.,  presence  of  gills  and  tail,  are  persistent  in  many 
batrachians,  &s  AxolotLfy  't*sfr****>&dt*st 

(2)  After  the  formation  of  the  neural  canal,  and  the  enclo- 
sure of  the  vitelline  sac  by  the  outer  germinal  layer  is  com- 
plete, a  fold  of  the  same  layer  arises  up  around  the  embryo 
(amniotic  fold)  which,  uniting  above,  forms  a  distinct  cavity 
(amnion),  in  which  is  contained  a  clear  fluid.  Soon  after  the 
development  of  this  cavity,  a  pouch-like  depression  of  the 
internal  layer  of  germinal  membrane  is  seen  to  one  side  of 
the  umbilical  sac  at  the  posterior  and  inferior  part  of  the 
visceral  cavity.  It  extends  outward  and  upward  parallel  with 
the  curve  of  the  amniotic  fold,  and  is  called  the  allantois.* 

Reptilia  and  Aves. —  Here  the  ova  are  developed  inde- 
pendent of  maternal  connection.  The  allantois  is  of  propor- 
tionately large  size,  covering  the  upper  portion  of  the  embryo 
and  lying  between  it  and  the  porous  shell.  It  is  at  once  a 
respiratory  and  excretory  organ  to  the  embryo. 

Mammalia. — Here  the  ova  are  borne  by  the  mother  either 
during  a  portion  or  the  whole  of  the  period  of  development; 
the  allantois  presenting  two  varieties  of  structure.  The  first 
of  these  is  of  comparatively  small  size,  and  free,  as  in  impla- 
cental  mammals.  In  the  second  the  organ,  often  completely 
surrounding  the  egg,  early  becomes  united  with  the  chorion, 
as  in  placenta!  mammals.  In  the  implacental,  the  chorion  is 
either  smooth  (Monotremata)  or  transversely  wrinkled  (Mar- 
supialia),  and  has  little  or  no  means  of  retention  to  the  uterine 
wall.  In  the  placental,  on  the  other  hand,  the  chorion  is 
shaggy  and  has  partial  or  entire  connection  with  the  analo- 
gous formation  of  the  mucous  membrane  of  the  uterus. 

The  placenta  is  the  organ  of  respiration  in  mammals,  as 

*  Prof.  Huxley  gives  a  different  account  of  the  formation  of  this  organ : 
"The  allantois  is  developed  much  later  than  the  amnion,  neither  from  the 
serous  nor  from  the  mucous  layers  of  the  germ,  but  from  that  intermediate 
stratum  whence  the  bones,  muscles,  and  vessels  are  evolved.  It  arises  as  a 
solid  mass  from  the  under  part  of  the  body  of  the  embryo  behind  the 
primitive  intestinal  cavity." 


GENERATION.  135 

the  allantois  is  in  reptiles  and  birds.  (See  Respiration, 
p.  62.) 

The  form  of  the  placenta  varies  in  different  orders  of 
Mammalia.  The  shaggy  coat  may  disappear  except  a  com- 
paratively small  circular  area  forming  discoidal  placenta,  as  in 
Bimana  (man),  Quadrumana  (monkey),  Cheiroptera  (bat),  In- 
sectivora  (mole),  Rodentia  (rat).  The  shaggy  coat  may  remain 
entire,  and  be  at  all  points  in  contact  with  decidua  vera,  and  is 
(1)  diffuse  with  cotyledons,  as  in  Ruminantia  (sheep),  or  diffuse 
without  cotyledons,  as  in  Omnivora  (hog),  Cetacea  (whale),  Edent- 
ata (sloth);  or  (2)  modified  in  the  form  of  a  ring  running 
transversely  round  the  fetus — zonular — as  in  Carnivora  (dog). 

In  implacental  mammals  the  young,  at  an  early  period,  is 
removed  from  the  uterus,  to  be  attached  to  the  nipple  of  a 
mammary  gland  within  an  inguinal  pouch,  as  in  Marsupialia,* 
or  in  the  absence  of  a  pouch,  after  a  manner  imperfectly  un- 
derstood, as  in  Monotremata. 

Mammary  gland. — This  is  a  cutaneous  gland  belonging  to 
the  racemose  type,  composed  of  aggregations  of  numbers 
of  simple  glands,  analogous  to  sebaceous  follicles.  Lacteal 
ducts  from  the  lobules  converge  to  a  central  space  to  form  a 
conical  spongy  prominence,  the  nipple  ('teat,'  'dug,'  'pap'). 

*  It  is  not  known  in  what  manner  the  embryo  is  transferred  from  the 
uterus  to  the  marsupium.  From  observation  made  upon  the  female  kanga- 
roo by  Prof.  Owen  at  the  Zoological  Gardens,  London,  in  1830,  it  was  shown 
that  the  removal  was  effected  during  night  of  the  thirty-ninth  day  of  gesta- 
tion. The  following  is  a  description  by  Prof.  Owen  of  the  embryo  on  the 
day  after  its  transfer  : 

"  The  new-born  kangaroo  was  attached  to  the  left  superior  nipple,  to  the 
point  of  which  it  adhered  pretty  firmly.  It  measured  one  inch  from  the 
mouth  to  the  root  of  the  tail,  was  quite  naked,  and  covered  by  a  thin  semi- 
transparent  vascular  integument;  the  place  of  attachment  of  the  umbilical 
cord  was  obscurely  indicated  by  a  longitudinal  linear  cicatrix.  The  forelegs 
were  longer  and  stronger  than  the  hind  ones,  and  the  digits  were  provided 
with  claws  ;  the  toes  were  developed  on  the  hind  legs :  the  body  was  bent 
forward,  and  the  short  tail  tucked  in  between  the  hind  legs.  This  little  ani- 
mal breathes  strongly,  but  slowly :  no  direct  act  of  sucking  could  be  per- 
ceived. Such,  after  a  gestation  of  thirty-eight  days,  is  the  condition  of  the 
new-born  young  of  a  species  of  kangaroo  of  which  the  adult,  when  standing 
erect  on  his  hind  feet  and  tail,  can  reach  to  a  height  of  seven  feet." 


136  COMPARATIVE   ANATOMY. 

Nipples  are  four  in  number  in  Macropus  (kangaroo),  concealed 
within  fissure  in  Cetacea,  absent  in  Ornithorhynchus.*  With 
some  mammals  the  glands  are  situated  in  the  ventral  region, 
as  in  Sus  (hog),  restricted  to  inguinal  region,  as  in  Ruminan- 
tia,  while  with  -others  they  are  exclusively  confined  to  the 
pectoral,  as  in  Cheiroptera  (bat),  Quadrumana,  and  man. 

*  The  cow,  ewe,  goat,  guinea-pig,  and  porpoise  have  one  tube  in  each  teat. 
The  pig  has  two,  the  rhinoceros  has  twelve,  and  the  hare  and  rabbit,  and  the 
cat  and  bitch  have  several.  In  the  Ruminantia  the  reservoirs  (ampullae)  are 
enormously  enlarged,  with  Carnivora  comparatively  small.  In  the  pig  there 
is  scarcely  any  reservoir ;  in  the  porpoise  the  great  enlargement  of  the  milk 
tube  is  a  substitute  for  the  reservoir.  (Astley  Cooper.) 


MEDICAL  ZOOLOGY. 


MAMMALIA, 

MOSCHUS  (Musk  Deer). — Order  Euraiuantia.    Family  Moschidse. 

Characters. — Placenta  cotyledonous.     Head  without  horns. 

Dental  formula:  mol.  6—6  ;  can.  1—0 ;  incis.  0—4;  incis.  0 — 4;  can.  1—0; 
mol.  6—6=14—20. 

Canines  conspicuously  developed  in  male  so  as  to  protrude  below  the 
level  of  the  lips.  Incisors  spatuliform,  arranged  in  a  continuous  series. 
Stomach  with  four  chambers.  Musk  sac  apparatus  present  in  male. 

M.  moschiferus,  Avicenna.  —  Head  small  and  short;  muzzle  pointed, 
naked,  and  blackish;  nostrils  crescentic,  very  open;  lower  lip  nearly  deprived 
of  hair ;  ears  large  ;  neck  thick  and  of  moderate  length ;  tail  very  short, 
thick,  conical,  and  soft ; — with  the  female  and  the  young  it  is  hairy  above 
and  woolly  beneath ;  while  that  of  the  male  of  the  second  year  is  entirely  naked 
and  red.  The  front  paws  are  so  short  that  the  distance  between  the  chest 
and  the  ground  is  less  than  that  comprised  between  the  withers  and  the  in- 
ferior face  of  the  thorax.  The  relation  between  the  anterior  and  posterior 
extremities  indicates  that  the  animal  is  adapted  for  leaping  rather  than 
walking.  Hoofs  small,  compressed,  subtriangular,  and  pointed.  Lateral 
(supplementary)  hoofs,  elongated,  but  not' reaching  the  ground.  The  thick- 
set appearance  of  the  musk  deer  depends  in  part  upon  the  nature  of  the  fur, 
which  upon  the  body  is  very  thick,  velvety.  Fur  thick,  short,  and  soft  about 
the  head  and  ears.  Upon  the  belly  or  each  side  of  the  umbilical  region 
longer,  becoming  more  slender,  and  forming  through  this  part  of  the  trunk 
a  large  pendant  tuft  in  front  of  the  thighs.  Upon  the  legs  it  is  short,  and 
especially  compact,  inferiorly.  The  general  color  of  animal  reddish-brown 
with  admixture  of  gray  and  white,  the  hues  varying  with  age  and  season. 
The  hair  is  always  white  at  the  base,  brown  or  gray  above  greater  or  less 
distance  of  the  shaft,  to  again  become  white  toward  the  tip.  This  variety 
of  coloring  gives  a  grizzled  appearance  to  the  whole  body.  Upon  the  claws 
the  hairs  become  shorter,  more  compressed,  and  of  a  darker  color  than  else- 
where. (Alphonse  Milne  Edwards.) 

Measurements.— From  muzzle  to  anus,  2'  11"  4'";  length  of  tail,  I"  2'"; 
length  of  head,  6"  2'";  length  of  ear,  3"4f"';  length  of  neck,  6"  6'";  height 

(137) 


138  MEDICAL   ZOOLOGY. 

of  anterior  part  of  body  from  back  to  hoof,  1"  10";  height  of  posterior  part 
from  rump  to  hoof,  2'  2"  6'".  (Pallas.) 

The  skeleton  bears  a  close  resemblance  to  that  of  Cervus  (deer).  Cer- 
vicals,  7;  dorsals,  14-15 ;  lumbars,  6.  Metatarsal  and  metacarpal  bones, 
two  in  number,  in  each  limb,  but  anchylosed  along  their  entire  length — a 
groove  more  apparent  in  posterior  than  the  anterior  limbs  indicating  the  line 
of  original  division.  The  former  bones  much  longer  than  the  latter.  The 
toes  articulate  by  distinct  condyles  to  the  'canon  bone,'*  each  toe  being 
composed  of  three  phalanges,  the  terminal  ones  being  hoofed.  Placed  in 
connection  with  the  '  canon  bone,'  two  supplementary  toes  are  seen,  as  in 
other  bi-sulcate  ruminants,  but  here  are  larger  than  usual,  project  downwards, 
each  composed  of  three  segments,  the  terminal  one  furnished  with  a  delicate 
hoof  closely  resembling  that  of  the  hog.  In  the  hind  limb  a  rounded  rudi- 
ment of  a  tarsal  bone  intervenes  between  the  first  phalanx  and  the  shaft  of 
the  '  canon.'  But  in  the  front  limb  the  corresponding  toe  is  in  relation  with 
a  bone  of  greater  size  in  the  form  of  a  conical  mass  which  is  firmly  secured 
to  the  canon  by  means  of  ligaments. 

The  disposition  of  the  viscera  agrees  in  its  main  features  with  that  of  the 
true  bi-sulcate  ruminants.  The  musk  apparatus  is  peculiar  to  the  male.  It 
is  situated  in  the  median  line  of  inguinal  region  midway  between  the  navel 
and  orifice  of  the  prepuce,  but  nearer  the  latter.  It  apparently  consists  of 
an  inversion  of  skin  at  the  position  of  the  prepuce,  forming  a  sac-like 
chamber  of  a  rounded  oval  shape,  flat  above,  convex  beneath.  It  is  longer 
than  wide,  and  rests  posteriorly  upon  the  penis,  for  the  reception  of  which 
it  presents  beneath  a  deep  median  groove.  Smooth  upon  its  superior  border, 
where  it  is  in  constant  contact  with  the  abdominal  muscle,  the  inferior  as- 
pect is  in  relation  with  the  skin.  The  sac  is  sparsely  covered  with  hairs, 
which  converge  obliquely  to  the  circular  excretory  opening. 

The  affinities  of  the  Moschidae  are  with  the  Cervidaef  and  Tragulidae.  J  They 
resemble  the  Cervidae  in  structure  of  canon  bone,  number  and  arrangement 

*  '  Canon  bone '  is  the  representative  of  the  metacarpus  in  the  anterior  and  the 
metatarsus  in  the  posterior  extremity. 

•j-  Cervidse. — Upper  canine  teeth  in  many.  Horns  cast  annually,  peculiar  to  males 
(in  females  none,  one  species  excepted).  Sebaceous  glands  in  front  of  eye.  A  soft 
layer  of  hair  at  the  hind  feet  in  most.  Tail  short,  sometimes  very  short.  (Van  der 
Hoeven.) 

J  Tragulidse.—  Placenta  diffuse.  Incisors  in  an  interrupted  series.  Space  in  median 
line.  Central  incisors  very  large,  with  wide  flattened  crowns.  Stomach  with  three 
chambers  only  (the  psalterium  being  absent).  Musk  sac  none. 

Genera.  Tragulua. — Metatarsal  and  metacarpal  bones  (os  canon)  nnited  in  median 
line.  Lateral  digits  well  developed,  and  prolonged.  Intermaxillaries  articulating 
with  the  nasal  bones.  Habitat. — Java  and  Sumatra. 

Hysemoschus. — Median  metacarpal  bones  distinct  throughout  life.  Mctatarsals  at 
first  distinct,  afterwards  become  united  in  median  line.  Lateral  digits  well  developed, 
robust,  and  attached  along  the  entire  length  of  the  median  metatarsals.  Intermax- 
illaries do  not  articulate  with  nasal  bones.  Habitat.— Africa.  (A.  Milne  Edwards.) 


MAMMALIA.  139 

of  incisor  teeth,  structure  of  stomach  and  placenta,  and  in  general  style  of 
movement  and  coloring ; — with  the  Tragulidae  in  absence  of  horns,  presence 
of  large  canine  teeth  in  the  males,  and  in  the  development  of  the  lateral 
digits.  This  last  feature — dependent  as  it  is  upon  others  in  the  anatomy  of 
the  extremities — recalls  the  construction  of  the  foot  of  the  hog.  The  relation 
of  the  musk  deer  to  the  hog  through  the  Hycemosckus  is  by  no  means  remote. 
Several  fossil  genera — Oreodon,  Anoplotherium,  etc. — apparently  connect 
the  Ruminantia  with  the  Omnivora. 

VIVERRA  (Civet  Cat). — Order  Carnivora.     Family  Yiverrina. 

A       A 

Characters. — Molars  mostly  —   -  three  false  on  each  side  in  upper  jaw, 
o — o 

three  or  four  in  lower.  Only  a  single  tuberculate  tooth  on  each  side  in 
lower  jaw  or  none.  Almost  always  two  tuberculated  teeth  on  each  side  of 
lower  jaw.  Feet  mostly  digitigrade,  either  pentadactylous  or  tetradactylous, 
with  claws  often  semi-retractile.  Back  of  tarsus  hairy.  Glandular  follicles 
between  anus  and  genitals  secreting  a  sebaceous  matter  of  disagreeable 
odor. 

Viverra.  Feet  pentadactylous,  with  claws  small,  curved,  semi-retractile; 
back  of  tarsus  and  underside  of  feet,  excepting  pads  of  toes  and  metatarsus, 
hairy  ;  body  slender,  head  elongate,  muzzle  acute,  legs  of  moderate  length, 
tail  conical,  generally  ringed  ;  back  crested  ;  orbit  incomplete. 

Dental  formula. — M.  2 — 2  ;  prem.  4 — 4 ;  c.  1 — 1 ;  in.  3 — 3 ;  in.  3 — 3  ;  c. 
1—1 ;  prem.  4—4;  m.  2—2=20—20. 

Vertebrae. — Cervical,  7 ;  dorsal,  13 ;  lumbar,  7.  ' 

V.  civetta,  Schreber. — Light  brownish-gray,  with  large  black  spots  ;  the 
tail  short,  long-haired,  with  some  whitish  spots,  at  the  tip  black ;  upon  the 
back  long  hairs  (mane). 

Measurements.— Length  of  body,  2'  9"  6'";  of  tail,  I7  3"';  head,  6";  ears, 
2".  Height  of  body  anteriorly,  11"  5'";  posteriorly,  10"  6"'. 

Habitat.— Africa,  from  31°  N.  lat.  to  25°  S.  lat. 

V.  zibetha,  Linn. — Light  brownish-gray  with  brown  spots ;  the  throat 
whitish,  with  oblique  dark  stripes  ;  tail  shorter  than  body,  short  haired,  with 
black  and  light  brown  rings.  (Van  der  Hoeven.) 

Measurements. — Length  of  body,  from  tip  of  nose  to  base  of  tail,  2'  5"; 
head,  5"  7"';  tail,  1'  3'". 

Habitat. — East  Indies. 

In  each  species  there  is  placed  on  either  side  of  the  opening  of  the  genital 
apparatus  an  oblong  sac,  with  thickened  walls,  presenting  upon  its  inner 
surface  openings  of  mucous  glandular  follicles,  in  which  is  secreted  the 
civet.  On  either  side  of  the  anus  a  pair  of  small  anal  glands  empty  a  fetid 
secretion. 

CASTOR  (Beaver).— Order  Rodentia.  Family  Sciuridae.  Sub-family  Cas- 
torinae. 


140  MEDICAL    ZOOLOGY. 

Characters. — A  double  claw  on  second  hind  toe.    Hind  feet  webbed.  Tail 

4 4 

broad,  flat  and  scaly.    Molars  -- — -,  complicated  or  folded,  with  one  groove 

rr 4 

on  the  inner  side  of  each  upper  molar,  and  three  on  the  outer,  and  vice  versa 
below;  the  anterior  molars  sometimes  with  more.  (Baird.) 

C.  canadensis,  Kuhl. — Head  large  and  broad ;  nussle  naked ;  nostrils 
lateral,  subcrescentic.  Upper  lip  acutely  emarginated,  though  scarcely  bifid. 
Eyes  small,  placed  midway  between  the  end  of  the  snout  and  the  auditory 
aperture.  Ears  of  moderate  size  (infra),  thick  and  nearly  orbicular,  densely 
covered  with  hair  on  both  surfaces.  Limbs  large  and  stout;  the  under  surfaces 
of  all  the  feet  entirely  naked ;  the  upper  surfaces  coated  with  short,  stiff  silky 
hairs  ;  the  fore  claws  are  about  as  large  as  hinder  ones.  Front  foot  with  five 
distinct  fingers,  each  armed  with  curved,  rounded  claw ;  third  finger  longest, 
the  fourth  a  little  shorter ;  then  in  order  to  second  and  fifth ;  the  claw  of  the 
first  reaches  as  far  as  the  cleft  between  the  third  and  fourth.  The  claw  of 
second  toe  possesses  a  claw-like  appendage.  There  are  only  two  tubercles  on 
the  palm,  both  large,  and  placed  side  by  side ;  the  exterior  twice  as  large  as 
the  interior,  and  extending  further  back.  Hind  feet  large,  their  plane  ob- 
lique to  body.  Toes  connected  by  thickened  naked  web  extending  between 
their  tips.  In  walking  the  whole  plantar  surface  touches  the  ground.  Tail 
conical  at  base,  where  it  is  densely  covered  with  hair,  but  suddenly  becomes 
very  flat  and  depressed.  It  is  for  the  greater  part  covered  with  transversely 
elongated  subhexagonal  scales  arranged  in  quincum  with  tolerable  regularity 
on  each  side.  Short  downy  hairs  project  between  the  scales,  obscuring  but 
not  concealing  them.  Fur  of  two  kinds;  upper  and  longer  hair  coarse, 
smooth,  and  glossy ;  under  coat  dense,  smooth,  and  silky.  Usual  color  red- 
dish brown ;  on  back  of  a  shiny  chestnut  color ;  on  the  under  surface  and 
around  mouth  and  throat,  a  shade  lighter ;  sometimes  quite  dark,  and  again 
of  rather  a  light  yellowish  tint  of  the  same.  (Baird.) 

Skull. — Facial  portion  but  little  smaller  than  brain-case,  narrow  between 
the  eyes.  Incisive  foramina  long  and  narrow,  occupying  rather  less  than 
one-third  of  interval  between  incisors  and  molars.  Zygomatic  arches  bold, 
thicker  in  centre  than  toward  extremities.  The  infraorbital  foramen  a  small 
slit,  gives  no  transmission  to  muscle ;  not  seen  from  the  side.  Ext.  auditory 
passage,  a  well-pronounced  tube,  directed  forward  and  outward.  The  lower 
jaw  with  articular  surface  broadly  oval,  the  coronoid  process  thick,  angle 
broad  and  rounded.  (Wagner's  Schreber.) 

Teeth. — Line  of  upper  molars  decidedly  convergent.  Palate  hollowed  out 
between  incisors  and  molars.  Inner  side  of  upper  molar  with  one  groove, 
the  outer  three;  this  being  reversed  in  the  lower  jaw,  which  shows  four 
grooves  on  the  inner  side.  The  anterior  molars  in  both  jaws  are  largest,  the 
rest  diminishing  backward  very  gradually;  the  anterior  molar  is,  however, 
longer,  proportionally,  than  the  corresponding  upper  one,  and  the  lower  line 
of  molars  exceeds  considerably  the  upper.  (Baird.) 

Cervical  vertebrae,  7;  dorsal,  14 ;  lumbar,  5;  sacral,  4 ;  caudal  28.    Thorax 


MAMMALIA.  .  141 

wide  and  bulging ;  seven  true  and  seven  false  ribs.  Sternum  of  seven 
pieces. 

The  glandular  accessories  to  the  mouth  are  numerous.  In  addition  to  the 
salivary  glands,  which  are  relatively  larger  than  in  any  other  rodent,  other 
follicles,  varying  from  fifty  to  sixty  in  number,  pour  a  slimy,  mucoid  secre- 
tion into  the  mouth.  A  spongy  mass  of  follicular  glands  occupies  a  portion 
of  the  mucous  membrane  along  the  lesser  curvature  of  the  stomach.  Caecum 
large;  anus  distinct  from  the  opening  for  genital  apparatus, — both,  how- 
ever, lie  within  a  common  cutaneous  depression. 

The  castoreum  sacs  are  found  in  both  sexes.  In  the  male  they  lie  near  the 
pubis,  are  oval,  flattened,  of  a  light  color  like  parchment,  and  communicate 
freely  with  one  another  by  their  transverse  portion.  (Ely.)  Each  measures 
from  2"-4"  in  length,  and  placed  alongside  the  elongated  prepuce,  into  which 
it  empties  by  a  distinct  opening.  The  walls  of  the  gland  are  composed  of  an 
external  fibrous  coat,  a  muscular  and  vascular  coat,  with  an  internal  mucous 
lining,  the  whole  being  bound  together  by  fibrous  processes  extending  in- 
ward. The  mucous  membrane  is  thrown  into  folds,  and  furnished  with  nu- 
merous scale-like  processes,  beneath  which,  in  relation  with  the  epithelium, 
the  castoreum  is  secreted.  Opening  into  the  depression  about  the  anus  are 
the  openings  of  several  pairs  of  anal  glands,  one  of  which  is  generally  par- 
tite or  larger  than  the  others.  (Brandt  and  Ratzeburg.)  They  elaborate  a 
fatty  secretion  with  no  properties  of  castoreum.  The  glans  penis  is  flattened. 
It  contains  a  bone  equal  to  its  length,  and  largest  at  its  base.  The  racemose 
glands  appended  to  urethra  are  analogous  to  Cowper's  glands. — In  the 
female  the  sacs  are  similarly  situated  to  those  of  the  male,  but  open  upon 
either  side  of  the  entrance  of  vagina.  (Ely.)  The  anal  glands  closely  resem- 
ble those  of  the  male. 

Measurements. — From  nose  to  root  of  tail,  23";  tail,  10";  from  heel  to 
end  of  middle  claw,  5"  6'";  breadth  of  tail,  3"  3'";  thickness  of  tail,  10"'; 
average  weight,  11^  ft>s.  (Aud.  and  Bachman.) 

Habitat. — North  America  from  Upper  British  America  to  Mexico ;  and 
Northern  Europe. 

HYRAX  (Daman,  Cony).  Order  Perissodactyla.    Family  Lamnungia. 

Characters. — Body  hairy,  bristles  on  face  around  nostrils  and  above  orbit ; 
long  setae  scattered  among  shorter  hairs  of  body.  Tubercle  in  place  of  tail. 
Dental  formula:  m.  4 — 3;  prem.  3 — 3;  c.  0 — 0;  in.  1 — 2;  in.  1 — 2;  c. 
0 — 0;  prem.  3 — 3;  m.  4 — 3=16 — 16.  A  single  small  false  molar  each  side, 
deciduous.  Crown  of  upper  molars  with  two  eminences  joined  by  a  crest  to 
the  outer  margin ;  crown  of  lower  molars  with  two  lunate  lines,  convex  out- 
wards. In  many  animals  two  very  small  canines. 

H.  capensis. — Head  small,  muzzle  short,  thick.  Form  heavy,  short,  and 
low  on  feet.  Ears  short,  round,  and  bordered  by  fine  hairs.  Neck  short, 
and  wider  than  long, — on  the  upper  lip,  beneath  eyebrows  and  throat,  are  a 
number  of  long  hairs.  Palms  of  feet  naked  and  covered  with  soft  skia 


142  MEDICAL    ZOOLOGY. 

Fore  feet  with  four  toes;  hind  feet  three;  these  toes  terminate  in  small 
rounded  hoofs,  excepting  the  innermost  toe  of  the  hind  foot,  which  is  armed 
with  an  oblique  hooked  claw.  Tail  a  mere  tubercle.  Three  mammae  on 
each  side  ;  the  anterior  is  axillary,  the  two  other  inguinal. 

Vertebrae. — Cervical,  7;  dorsal,  20-21 ;  lumbars,  8;  caudal,  6.  Stomach 
divided  into  two  chambers ;  caecum  very  large,  and  colon  with  numerous  dila- 
tations, with  two  caecal  appendages  recalling  those  of  certain  birds.  (Cu- 
vier.)  The  hyrax  has  close  affinities  with  Rhinoceros.  The  latter  animal 
differing  in  being  naked,  in  each  foot  having  three  toes,  and  in  the  horn-like 
appendage  to  nose. 

The  hyrax  yields  hyraceum.  Its  origin  is  not  certainly  known.  From 
analysis,  it  would  appear  to  be  derived  from  the  urine  and  faeces. 

CATODON  (Spermaceti  Whale).  Nostrils  longitudinal,  parallel  or  diverg- 
ing, covered  with  a  valve,  often  larger  and  more  developed.  Pectoral,  broad, 
truncate.  Fingers,  5.  Fhyseteroidia. 

Family  3 — Catodontidae. — (Head  large,  subcylindrical,  blunt.  Lower  jaw 
narrow.  Teeth  large,  in  the  lower  jaw  only,  fitting  into  pits  in  the  gums  of 
the  upper  one.  Nostrils  separate,  one  often  abortive.  The  hinder  edge  of 
the  maxillary  elevated,  forming  a  concavity  on  the  forehead  of  the  skull. 
Pectoral  broad,  truncated.  Fingers  5.  Eye  and  limb  left  side  smaller; 
left  nostril  very  large.  The  lower  jaw  is  early  joined  in  front  into  a  sub- 
cylindrical  mass  ;  the  branches  converge  and  are  nearly  straight.) 

Catodon.  Head  rather  compressed  in  the  front  and  truncated,  with  the 
blowers  close  together  in  the  front  of  the  upper  edge,  separated  from  the 
head  by  an  indentation.  Nose  of  skull  elongate,  broad,  depressed.  Lower 
jaw  shorter  than  the  upper  one,  very  narrow,  cylindrical  in  front,  and  the 
rami  united  by  a  symphysis  for  nearly  half  its  length.  Back  with  a  roundish 
tubercle  in  front  over  the  eyes,  called  the  'bunch,'  and  a  rounded  ridge  of 
fat  behind,  highest  in  front  over  the  genital  organs,  called  the  '  hump,'  and 
continued  in  a  ridge  to  the  tail.  No  true  dorsal  fin.  Pectoral  broad,  trun- 
cated. Teeth  conical,  often  worn  down.  Males  larger  than  females.  The 
atlas  is  distinct;  the  other  cervical  vertebrae  are  soldered  together.  (Gray.) 

(7.  macrocephalus. — The  northern  sperm  whale. 


REPTILIA.  143 


KEPTILIA, 

OPHIDIA. — Cold-blooded  vertebrates  having  palatine  bone  united  with 
pterygoid  bone  only.  Continuity  of  parietal  and  sphenoid  bones  complete. 
Kami  of  lower  jaw  united  by  ligament.  Eyes  with  simple  epidermic  eyelids. 
(Cope.) 

Prominent  Anatomical  Features. — Limbless  ;  bodies  of  vertebrae  articu- 
lated by  ball-and-socket  joints.  Progression  effected  by  muscular  action 
upon  the  abdominal  scales  and  ribs. 

Disposition  of  internal  organs. 

The  tongue  exsertile,  generally  bifid. 

Solenoglypha. — Superior  maxillary  short,  united  to  prefrontal.  Tympanic 
bone  elongated.  Fangs  without  external  canal.  Pupils  elliptical.  Occipital 
region  scaly.  (Cope.) 

(1)  Crotalidae. — Erectile  poison  fangs  in  front.  Few  teeth  in  upper  jaw. 
A  deep  pit  between  eye  and  nostril.  Head  scaly. 

Caudisona. — Upper  surface  of  head  covered  with  small  plates,  scale-like, 
with  a  few  larger  ones  in  front.  The  tail  is  terminated  by  a  well-developed 
rattle.  Subcaudal  scutellae  entire.  Temporal  and  labial  shields  small  and 
convex. 

C.  horrida  (rattlesnake),  Linn. — Head  angular.  Scales  between  the  su- 
perciliaries  small,  numerous,  uniform.  Plates  above  snout,  2  anterior  frontal 
and  5  post  frontal.  Suborbital  chain  continuous,  of  large  scales.  Two  rows 
between  this  and  labials.  Labials  12-14  above,  5th  largest ;  13-15  below. 
Scales  on  the  back  23-25,  all  carinated ;  carination  on  outer  row  obsolete.  Tail 
black.  Above  sulphur-brown,  with  two  rows  of  confluent  brown  lozenges. 
Light  line  from  superciliary  to  angle  of  mouth.  Behind  this  a  dark  patch. 
Battle  acuminate. 

Habitat. — North  America,  warm  rocky  exposures. 

Other  Species.     C.  durissa  (Eastern  rattlesnake). 

C.  confluenta.     Western. 

C.  lucifer.     California. 

C.  atrox.    Texas. 

Crotalus,  Linn. — Upper  surface  of  the  head  covered  with  nine  large  plates. 
The  tail  terminates  in  a  rattle,  generally  smaller  than  in  Caudisona.  Sub- 
caudal  scutella  entire,  except  a  few  at  the  end  of  the  tail,  which  are  bifid. 

C.  miliaris,  Hall  —Twenty-two  or  twenty-three  dorsal  rows  of  scales,  all 
of  which  are  carinated,  the  lateral  and  first  rows  but  slightly ;  a  vertebral 
brownish-red  line ;  seven  series  of  blotches,  one  dorsal  and  three  lateral,  on 
each  side,  the  uppermost  of  which  is  obsolete  and  the  lowest  subject  to 
irregularities.  Vertical  plates  subcordiform,  occipital  oblong  and  elongated. 
A  narrow  white  line  commences  at  the  lowest  point  of  the  orbit  and  passes 
obliquely  backward  to  angle  of  mouth. 

Habitat. — Southern  States. 


144  MEDICAL    ZOOLOGY. 

Other  Species.  C.  consors  (Kansas).  C.  tergeminus  (Western  States). 
C.  edwardsii  (New  Mexico  and  Texas).  C.  kirtlandii  (Western  States). 

Ancistrodon.  Nine  plates  on  top  of  head.  No  rattle.  One  pair  of  oc- 
cipitals  ;  larval  between  the  nasal  and  anterior  orbitals.  Labials  excluded 
from  orbit  by  the  presence  of  suborbital  plates.  Scales  carinated ;  rows  23 
in  number.  Subcaudal  scutellae  divided  posteriorly.  Sometimes  a  small 
plate  between  the  vertical  and  post  frontal. 

A.  contortrix  (Copperhead),  Baird  and  Girard. 

Loral  plate  present.  Labials  not  entering  into  orbit.  Dorsal  rows  of 
scales  23.  Color  light  chestnut,  with  inverted  darker  blotches  on  the  sides. 
Labials  yellowish  white. 

Habitat.— United  States.    Terrestrial. 

A.  piscivorus  (Water  moccasin),  Baird  and  Girard. 

No  loral.  Inferior  wall  of  orbit  constituted  by  third  labial ;  25  dorsal 
rows.  Dark  chestnut  brown,  with  indistinct  vertical  dark  bars.  Line  from 
superciliary  along  edge  of  head  through  middle  of  second  supralabial  row. 
A  second  line  from  the  lowest  point  of  the  orbit  parallel  to  the  first. 

Habitat. — United  States.     Aquatic. 

(2)  Yiperidae.  No  pit  on  side  of  face.  Head  plated.  Upper  jaw  toothless, 
with  large  fangs  in  front ;  lower  toothed.  Ventral  shields  broad,  band-like. 
Head  large  behind ;  subcaudal  scutes  single. 

Vipera  (Viper).  Vertebral,  occipital,  and  superciliary  plates  sometimes 
distinct ;  front  of  head  with  small  shields ;  nose  blunt. 

V.  berus. 

V.  aspis. 

Habitat. — Western  and  Southern  Europe.  (Gray.) 

Cerastes. — Subcaudal  plates  two-rowed ;  nostrils  lunate,  in  the  hinder  part 
of  a  small  nasal  plate ;  superciliary  shields  very  small,  scale-like.  Scales 
keeled,  broad,  ovate,  rounded  at  end,  placed  in  oblique,  cross  series ;  keel 
not  reaching  the  tip.  (Gray.)  (7.  cornutus.—N.  Africa. 

Proteroglypha. — Maxilla  horizontal,  thickened,  and  not  reaching  premaxil- 
laries  anteriorly,  in  contact  with  prefrontal,  bearing  a  perforate  and  usually 
grooved,  immovable  tooth.  Head  generally  quadrangular,  with  flat  crown 
and  moderate  or  short  muzzle.  Loral  plate  none.  (Cope.) 

Naja. — Head  high,  quadrangular,  not  very  distinct  from  neck,  with  rather 
short,  rounded  muzzle.  Rostral  moderate,  rounded,  sometimes  produced 
backwards  and  pointed ;  anal  scutes  entire ;  subcaudal  two-rowed ;  one  or 
two  fangs  behind  large  anterior  teeth,  not  grooved. 

N.  Tiaje  (Cleopatra's  asp),  Seba. — Sixth  upper  labial  united  with  tempo- 
rals, and  forming  a  very  large  shield  in  contact  with  oculars  ;  generally  with- 
out marks  on  neck. 

Habitat. — Northwestern  Africa 

N.  tripudians  (Cobra  di  capello),  Scheuz. 

Sixth  upper  labial  small,  forming  a  suture  with  a  very  large  temporal ; 
generally  with  a  spectacle  mark  on  neck. 


PISCES.  145 

Habitat. — East  Indies. 

Hydrophis,  Daud. — Rostral  plate  broad,  transverse;  lower  triangular; 
nasal  truncated  or  notched  in  front ;  ventral  shield  flat ;  head  short ;  eyes 
small. 

H.  obscura  (Sea  snake). — East  Indies. 


PISCES, 

GADUS  (Cod).  Order  Jugulares.  Family  Gadidae.  Characters.— Body 
elongate,  but  little  compressed,  covered  with  soft  scales  not  very  volumin- 
ous ;  head  well  proportioned  and  without  scales ;  fins  soft ;  jaws  and  front 
of  vomer  armed  with  pointed,  irregular  teeth,  middling  or  small-sized,  in  sev- 
eral rows,  forming  a  sort  of  curry-comb  or  rasp  ;  gills  large,  with  seven  rays. 
Fins.  Ventrals  separate,  jugular;  generally  with  two  or  three  fins  on  back ; 
one  or  two  behind  anus  ;  and  distinct  caudal.  Stomach  in  form  of  a  large, 
strong  sac;  caeca  numerous  and  long;  air-bladder  large,  with  thick  walls 
(without  duct),  and  often  dentated  upon  sides.  (Cuvier.) 

G.  morrhua,  Linn. — Barbel  rather  long,  as  long  as,  or  longer  than  the 
eye,  which  is  one-seventh  of  the  length  of  the  head,  and  one-half,  or  rather 
more  than  one-half,  of  the  width  of  the  interorbital  space.  Snout  more 
than  twice  as  long  as  the  eyes,  obtuse,  with  the  upper  end  longest.  The 
height  of  the  body  is  less  than  the  length  of  the  head,  which  is  two-sevenths 
of  the  total  (without  caudal).  The  vent  is  situated  vertically  below  the  an- 
terior rays  of  the  second  dorsal.  The  two  anal  fins  separated  from  each 
other  by  an  interspace.  Proportions  of  the  fins  : 

ID.  2D.  3D.  1A.  2  A. 

1  i_3  i_i  i_2  1—0-9 

Greenish  or  brownish  olive,  with  numerous  yellowish  or  brown  spots  on  the 
back  and  on  the  side. 

Swim  bladder  large,  broad,  and  having  at  its  anterior  extremity  a  worm- 
like  process,  which  is  held  in  relation  to  the  muscles  of  the  vertebral  column. 
At  the  upper  third  of  the  interior  surface  of  the  bladder  a  congerie  of  vessels 
(wonder  net)  is  seen,  giving  a  reddish  color  to  the  lining  membrane.  Kidneys 
of  a  blackish  red,  thickest  at  upper  portions.  Urinary  bladder  small,  with  two 
appendages.  Spleen  long,  small,  triangular.  Liver  of  a  clear  yellow  color, 
very  large,  of  three  lobes,  the  smallest  of  which  lies  beneath  the  stomach. 
Gall  bladder  in  the  middle  of  the  right  lobe.  (Brandt  and  Eatzeburg.) 

Habitat. — The  cod  is  found  in  the  seas  of  the  northern  hemisphere  from 
the  fortieth  to  the  seventy-fifth  degree.  Coast  of  North  Europe,  Iceland, 
and  Greenland,  southward  to  New  York.  (Giinther.) 

ACIPENSER.    Class  Ganoidei  (Muller).     Fishes  with  tabular  or  angular 

10 


146  MEDICAL    ZOOLOGY. 

scales,  or  perfectly  naked.  Tail  apt  to  be  heterocercal ;  opercular  gill  in 
many;  several  valves  in  the  arterial  trunk;  optic  nerves  not  decussating ; 
spiral  valve  in  intestine ;  swimming  bladder  and  air  tube  ;  skeleton  generally 
cartilaginous;  ventral  fins  abdominal.  (Thymus  gland  in  sturgeon  and 
shark.) 

Acipenser. — Sqiialoid ;  dorsal  and  anal  fins  opposite;  pancreas  conglom- 
erate; one  gill  opening;  no  rays.  "Upper  jaw  formed  by  palatine  bones, 
firmly  united  to  the  maxillary;  intermaxillary  rudimentary."  (Storer.) 

Mouth  toothless.  Operculum  surrounded  by  a  semicircular  fold  of  integ- 
ument. Head  more  or  less  distinctly  quadrangular  or  club-shaped,  the  bones 
of  the  skin  concealed  by  a  number  of  superficial  plates.  Eyes  and  nares  to 
side  of  head.  The  latter  are  two  in  number  on  either  side,  superior  rounded, 
inferior  elliptical.  Muzzle  produced,  furnished  beneath  with  four  barbels. 
Malar  bone  (!)  rightangular,  outer  half  covered  with  bones  of  the  exoskeleton 
surrounding  the  posterior  part  of  the  orbital  opening.  Mouth  transversely 
oval,  placed  behind  the  eyes,  upon  the  under  side  of  the  muzzle,  in  a  depres- 
sion. Under  lip  cleft  in  middle.  Body  long,  covered  with  small  scales  or 
plates,  skin  rarely  smooth,  furnished  with  five  rows  of  dermal  plates,  com- 
monly assuming  a  pentangular  form.  One  row  occupies  the  median  line  of 
back,  two  others  (one  on  either  side)  lie  directly  behind  this,  starting  from 
the  region  of  shoulder-blade  and  extending  along  the  lateral  aspect  of  body; 
and  two  (one  on  either  side)  extending  from  base  of  coracoid  bones  along  the 
ventral  region.  The  dermal  plates  composing  these  lines  are  largest  above, 
smallest  beneath.  Anal  fin  near  caudal.  Ventral  fin  nearer  anal  than  pectoral. 
Dorsal  fin  about  opposite  anal.  Caudal  fin  heterocercal,  unequally  forked, 
the  upper  portion  being  the  larger.  Branchial  arches  five.  The  swimming 
bladder  communicates  with  the  stomach.  Pancreas  consisting  of  a  single 
mass.  Intestine  furnished  with  spiral  folds. 

The  sturgeon  is  a  fresh  water  fish.  It  is  found  in  the  rivers  of  Northern 
Europe,  Asia,  America,  and  Western  Africa.  It  may  at  times,  however, 
descend  to  the  sea. 

1.  A.  rubicundus,  Les.— Body  ruddy;   flat  between  eyes;  lateral  semi- 
plates  oblique  39  ;  4  feet  long.     Great  Lakes,  U.  S. 

2.  A.  brevirostrzs,  Mitch. — Snout  blunt  and  short;  dorsal  scutes  9-12; 
lateral  23-29 ;  length  2-5  feet.    Eastern  Rivers,  U.  S. 

3.  A.  oxyrhyncus,  Mitch. — Snout  elongated,  spatula-like,  covered  with 
strong  bony  plates ;  length  2-7  feet.    Eastern  Rivers,  U.  S. 

4.  A.  huso.  Northern  Russia. 


INSECTA.  147 


INSEOTA, 

CANTHARIS.*  Vesicating  or  blistering  insects  are  those  having  the  power, 
when  locally  applied,  of  exciting  that  form  of  inflammation  terminating  in 
a  copious  formation  of  serum  under  the  cuticle.  Very  many  species  possess 
this  peculiar  power,  all  belonging  to  the  large  Order  called  Coleoptera  or 
Beetles.  The  name  '  fly,'  as  applied  to  them,  is  altogether  a  misnomer,  tiies 
having  but  two  wings  and  a  suctorial  mouth,  while  beetles,  in  addition  to 
their  wings,  have  wing-cases  or  elytra  and  a  masticatory  mouth. 

CLASSIFICATION. 

The  vesicants  form  by  themselves  a  family  in  the  great  order  of  beetles, 
and  belong  to  that  section  characterized  by  heteromerous  tarsi ;  that  is,  the 
four  anterior  feet  or  tarsi  are  five-jointed  and  the  posterior  pair  four- 
jointed. 

From  all  other  heteromerous  beetles  they  maybe  distinguished  by  the  an- 
terior coxal  cavities  being  open  behindhand  the  coxa3  themselves  prominent, 
the  head  constricted  behind,  and  the  claws  of  the  tarsi  cleft  or  toothed.  The 
thorax  at  base  is  always  narrower  than  the  elytra.  The  family  thus  consti- 
tuted is  called  MELOID.E,  and  is  divided  into  two  tribes,  as  follows : 

Side  pieces  of  meso-  and  metathorax  covered  by  elytra         .  MELOINI. 
Side  pieces  of  meso-  and  metathorax  not  covered  by  elytra  .  LYTTINI. 

The  first  tribe  contains  five  genera  in  our  country,  distinguished  from 
each  other  by  the  following  characters  : 

Elytra  short,  imbricated MELOE. 

Elytra  not  imbricated. 

Elytra  shorter  than  abdomen. 

Elytra  strongly  divergent .        .         ...        .  MEGETRA. 

Elytra  contiguous  at  basal  fourth      .         .        .  NOMASPIS. 
Elytra  nearly  or  totally  concealing  abdomen  above. 

Elytra  connate,  much  inflated  .        .  .  CYSTEODEMUS. 

Elytra  sub-connate  pubescent    ....  HENOUS. 

The  insects  of  this  tribe  are  all  without  wings,  and  will  consequently  never 
be  taken  in  flight.  Species  of  Meloe  are  found  in  all  parts  of  our  country. 
In  early  spring  they  occur  under  stones,  while  later  in  the  season  great  num- 
bers are  frequently  met  with  on  certain  favorite  plants.  They  are  all  either 
dull-black  or  bluish  black,  seldom  with  any  lustre,  and  in  many  species  the 
males  have  the  antennae  distorted.  Megetra  is  New  Mexican.  The  two 

*  Contributed  by  Dr.  Geo.  H.  Horn. 


148  MEDICAL   ZOOLOGY. 

known  species  have  very  rugose  elytra,  with  a  more  or  less  irregular  yellow 
stripe  ;  otherwise  they  are  black,  with  the  head  sometimes  red.  Nomaspis 
occurs  in  Colorado ;  it  resembles  Meloe.  Cysteodemus  contains  two  species, 
the  most  singular  of  the  family.  The  elytra  are  much  inflated  and  deeply 
pitted  ;  in  one  species  dull-blue,  and  in  the  other  more  brilliant  in  color.  They 
are  found  in  the  southern  deserts  of  California  and  Arizona.  One  species  at 
least  is  excessively  abundant,  and  possesses  moderate  power  as  a  vesicant. 
Henous  occurs  on  our  western  plains  and  in  Texas.  It  is  deep  black  in 
color,  and  the  only  pubescent  species  in  the  group. 

The  second  tribe  of  the  family,  Lyttini,  contains  by  far  the  greater  num- 
ber of  species  and  genera,  the  latter  numbering  already  sixteen  in  our 
own  country,  divided  into  three  sub-tribes. 

Front  of  head  not  prolonged  below  insertion  of  antennae  .  HORIINI. 
Front  prolonged,  frontal  suture  evident. 

Mandibles  prolonged,  acute       ....  NEMOGNATHINI. 

Mandibles  obtuse,  short     .        .        .        .        .        .  LYTTINI. 

The  first  sub-tribe  contains  rare  species,  the  one  found  in  the  eastern  re- 
gions is  black  with  red  wing-cases,  and  though  destitute  of  wings,  has  been 
seen  flying  by  means  of  the  elytra  albne.  All  belong  to  the  genus  Trierania. 
The  Nemognathini  are  divided  into  three  genera : 

Maxillae  with  the  outer  lobe  prolonged. 

Antennae  not  thickened  externally     ....  NEMOGNATHA. 

Antennae  thicker  towards  tip,  thorax  conical     .        .  GNATHIUM. 

Maxillse  with  the  outer  lobe  not  prolonged       .        .        .  ZONITIS. 

The  prolongation  of  the  maxillae,  in  the  first  two  genera,  is  a  curious  char- 
acter, and  enables  the  insect  to  obtain  its  food  from  the  flowers  on  which  it 
lives  in  the  same  manner  as  bees  and  suctorial  insects  generally.  These  in- 
sects are  for  the  most  part  western,  occurring  abundantly  on  the  plains  and 
in  California  on  flowering  plants.  The  sub-tribe,  Lyttini,  contains  twelve 
genera,  divided  into  four  groups  : 

Yertex  not  elevated. 

Second  joint  of  antennae  long  .        .        .  .  MACROBASES. 

Second  joint  of  antennas  much  shorter  than  third  .  LYTT^E. 
Yertex  elevated. 

Antennas  filiform,  of  moderate  length       .         .  .  EUPOMPH^E. 

Antennae  very  short,  not  longer  than  head       .  .  PHODAG^I. 

The  group  Macrobases  contains  two  genera,  Macrobasis  with  wings,  and 
Apterospasta  without.  They  contain  some  of  our  largest  species.  The  third 
and  fourth  groups  contain  each  one  genus  and  species,  and  are  of  such 
rarity  as  never  to  have  been  experimented  with.  They  are  found  in  Arizona 
and  California  in  desert  regions.  The  Lyttae  are  more  numerous,  and  form 
eight  genera : 


INSECTA.  149 

Penultimate  joint  of  tarsi  bilobed        ....  TETRAONYX. 
Penultimate  joint  of  tarsi  cylindrical. 

Lower  portion  of  claws  equal  to  upper. 

Anterior  thighs  with  a  sericeous*  hairy  spot. 
Second  joint  of  antennae  equal  to  half 

the  third PLEUROPOMPHA. 

Second  joint  of  antennae  very  short         .  EPICAUTA. 
Anterior  thighs  glabrous,  no  sericeous  spot. 

Antennae  filiform,  outer  joints  cylindrical   PYROTA. 
Antennae  thicker  externally,  outer  joints 
rounded. 

Labrum  deeply  emarginate      .        .  POMPHOP(EA. 
Labrum  slightly  emarginate     .        .  LYTTA. 
Lower  portion  of  claws  shorter  than  upper. 

Labrum  not  emarginate,  body  pubescent        .  CALOSPASTA. 
Labrum  emarginate,  body  not  pubescent        .  TEGRODERA. 
By  the  above  table  of  characters,  all  the  genera  from  our  own  and  neigh- 
boring countries  may  be  recognized.     Lytta  is  equivalent  to  Cantharis  of 
older  authors,  the  latter  name  having  been  dropped  on  account  of  the  confu- 
sion of  species  adopted  at  various  times  as  its  type.  As  several  of  the  above 
genera  are  rare,  even  in  the  cabinets  of  entomologists,  it  would  be  well  to 
notice  from  among  them  various  species  capable  of  being  used  in  medicine 
as  a  substitute  for  the  Lytta  vesicatoria  of  Europe. 

Macrobasis  fabricii  is  our  common  American  species,  nearly  one-half  inch 
long,  found  on  various  plants  during  the  early  summer  months,  in  all  parts  of 
the  country.  The  color  is  ashy  gray  with  darker  antennae. 

M.  luteicornis  is  a  large  Texan  species,  occurring  in  very  great  abundance 
when  found.  It  is  of  a  light  ashy-gray  color,  with  reddish-brown  antennae, 
the  first  joint  being  (in  the  males)  large  and  broad. 

Epicauta  vitatta  is  our  common  potato  fly,  and  occurs  abundantly  during 
June  and  July  on  the  potato  and  tomato  plants.  It  is  an  elongated  insect, 
black  in  color,  with  yellowish  stripes  on  the  thorax  and  elytra.  This  insect 
must  not  be  confounded  with  the  potato  bug  of  the  West,  a  short,  robust 
insect  of  a  different  group  and  not  at  all  vesicant. 

Epicauta  Pennsylvania  is  smaller  than  the  above  and  totally  black. 
Epicauta  ferruginea  and  maculata  are  found  abundantly  in  the  plains  of 
the  West ;  the  latter  is  gray,  with  black  spots,  the  former  ferruginous  in 
color ;  both  are  small. 

Pyrota  contains  many  moderate  or  large  species,  characterized  by  a  yel- 
low body  and  legs ;  the  elytra  have  large  spots  or  bands  of  black.  These 
all  occur  in  our  Southern  States  and  have  good  vesicatory  power. 

Pomphopcea  contains  several  species,  occurring  rarely  in  abundance. 
They  all  haVe  aeneous  elytra  and  yellow  legs.  One  species  is  occasionally 

*  Sericeous — covered  with  a  fine  silken  recumbent  pubescence. 


150  MEDICAL   ZOOLOGY. 

injurious  to  pear-trees,  and  has  been  collected  and  used  medicinally  with  most 
excellent  effect. 

Lytta  contains,  besides  the  vesicatoria  of  Europe,  many  species  in  all 
parts  of  the  world,  and  all  the  species  thus  far  tried  have  proved  efficacious. 
In  our  own  country  every  section  affords  species,  and  many  are  large  and 
beautiful. 

Lytta  nuttalU  is  a  very  abundant  species  on  the  plains  and  in  Oregon.  It 
resembles  the  vesicatoria  so  closely  as  to  have  been  mistaken  for  it.  It  was 
reported  by  one  of  the  early  government  expeditions  that  bushels  could  have 
been  collected  at  one  place,  and  that  many  were  swept  up  and  destroyed  to 
afford  room  for  camping  purposes.  This  is  no  exaggeration,  as  I  have  seen, 
in  Calfornia,  many  hundreds  of  thousands  that  could  have  been  gathered  in 
very  few  minutes.  Lytta  nuttalli  could  readily  be  substituted  for  the  vesica- 
toria and  would  defy  detection  either  by  the  color  of  the  powder  or  by  its 
effects. 

Lytta  vulnerata  and  melazna  are  found  in  California  and  are  those  spoken 
of  above.  Numerous  experiments  have  been  tried  with  them,  internally  and 
externally,  and  the  full  effect  of  the  medicine  produced.  Many  species  could 
be  enumerated  from  all  parts  of  our  territory,  but  as  they  all  possess  the 
same  qualities,  the  few  above  named  will  suffice. 

Tegrodera  erosa  is  a  beautiful  species  found  in  California,  the  head  and 
thorax  red  and  elytra  yellow  with  two  black  bands,  one  terminal,  the  other 
median ;  the  surface  is  eroded  or  with  a  raised  network. 

SEAT    OF    VESICATING    POWER. 

This  matter  has  long  been  the  subject  of  conjecture,  and  to  Prof.  Joseph 
Leidy  is  due  the  credit  of  experimenting  with  more  satisfactory  results  than 
any  preceding  investigator.  Cantharidin  had  long  been  known  as  the  active 
agent,  even  before  these  experiments.  A  full  account  is  published  in  the 
Am.  Jour.  Med.  Sciences  for  Jan.  1860,  and  Jour.  Pharmacy,  March,  1860. 
In  these  papers  it  will  be  found  that  the  blood  is  the  most  effective,  then 
certain  glands  or  appendages  of  the  generative  system,  and  finally  the  eggs. 
From  this  it  will  be  seen  that  the  greater  portion  of  the  body,  if  deprived  of 
blood,  would  be  totally  inert.  The  power  of  the  blood  may  be  realized  by 
any  one  collecting  these  insects.  They  have  the  habit  of  causing  the  rup- 
ture of  certain  of  their  ligaments,  particularly  at  the  knee-joint,  from  which 
a  drop  will  issue  capable  of  producing  a  large  blister  on  tender  skin.  The 
question  has  occasionally  been  raised  as  to  whether  certain  of  our  species 
did  not  produce  more  unpleasant  effects  on  its  external  application  than  the 
foreign  one.  There  can  be  but  little  truth  in  such  suppositions.  I  have  used 
very  many  of  our  native  species  medicinally,  and  have  experimented  on  my 
own  person  with  many  others,  and  can  notice  no  difference.  There  can  be  ^ 
no  doubt  that  our  natives  are  at  times  the  more  active  and  rapid  in  action.  J 
This  can  be  attributed  to  the  freshness  of  the  specimens  made  use  of,  as  the 
imported  article,  particularly  in  powder,  is  apt  to  deteriorate. 


INSECTA.  151 

The  early  history  of  the  Meloidae  is  extremely  interesting.  The  female 
deposits  the  egg  upon  flowers.  The  egg  shortly  hatches,  and  a  small  louse- 
like  insect  makes  its  appearance,  which  very  soon  attaches  itself  to  the  body 
of  some  bee  or  wasp  and  by  it  is  carried  to  its  nest.  The  parasite  then  leaves 
the  parent  wasp  and  feeds  at  the  expense  of  the  young,  and  after  undergoing 
several  metamorphoses  assumes  the  state  of  pupa  preparatory  to  becoming 
a  fully  developed  insect. 

Besides  the  true  vesicants,  other  insects  and  spiders  have  been  said  to  pro- 
duce vesication.  These  matters  have  not  yet  been  sufficiently  investigated 
to  pronounce  upon  their  truth.  The  insects  that  have  been  thus  used  are 
comparatively  rare,  and  not  at  all  available  as  substitutes  for  our  more  com- 
mon Meloides. 

Species  of  other  genera  than  those  mentioned  in  the  above  notes  are  oc- 
casionally used  in  other  parts  of  the  world,  as  Mylabris,  Cerocoma,  etc.; 
but  as  these  are  but  rarely  brought  to  this  country,  they  deserve  no  more 
than  a  passing  notice.  The  preceding  tables  have  been  prepared  solely  in 
regard  to  North  American  entomology.  Species  of  many  of  these  genera 
occur  in  other  parts  of  the  world,  as  well  as  species  of  very  nearly  as  many 
more  genera  as  are  here  enumerated. 

ACANTHIA  (Bedbug).  Fabricius. — Order  Hemiptera.  Mouth  suctorial, 
haustellate;  wings  two  in  number,  and  two  wing  covers  or  hemelytra. 
Exceptions  sometimes  occur  in  which  the  wings  and  cases  are  rudimentary 
or  even  absent.  Sub-order  Heteroptera.  Section  Geocores  (antenna  equal 
to  half  the  length  of  the  body).  Family  Ductirostres  (beak  received  in  a 
groove  and  the  front  without  ocelli). 

Characters. — Body  flat;  antennae  terminated  abruptly  in  a  slender  bristle. 

A.  lectularia,  Linnaeus. 

The  bedbug  has  an  oval  body,  nearly  one-fourth  inch  in  length,  somewhat 
narrow  at  the  head,  much  flattened,  and  of  a  reddish  or  ferruginous  color. 
It  is  covered  with  a  very  fine  pubescence.  The  head  is  quadrate,  with  a 
slight  lobe  in  front  hiding  the  base  of  the  rostrum.  The  eyes  small  and 
round.  The  antennae  filiform,  of  but  four  joints,  of  which  the  first  is  very 
short.  The  thorax  is  slightly  excavated  anteriorly  and  truncate  behind ;  the 
sides  are  rather  broadly  dilated  and  semi-membranous.  There  are  no  true 
wings,  and  but  short  rudimentary  hemelytra.  The  legs  are  moderate  in  size, 
rather  slender;  the  tarsi  are  short,  three-jointed,  of  which  the  first  and  third 
are  very  small,  the  latter  furnished  with  two  strong  hooks.  The  abdomen  is 
broadly  oval,  composed  of  eight  segments,  and  fimbriated  at  its  margin,  and 
generally  tipped  with  black  posteriorly. 

The  odor  of  these  insects  is  not  characteristic,  but  is  found  in  many  other 
Hemiptera,  and  is  the  secretion  of  a  gland  in  the  metathorax  opening  between 
the  hind  legs. 

Their  eggs  are  laid  during  the  warm  months,  and  when  they  are  hatched 
the  young  represent  the  old  in  miniature,  without  the  rudimentary  hemelytra. 

The  mouth  consists  of  a  short  three-jointed  rostrum  which,  when  at  rest, 


152  MEDICAL   ZOOLOGY. 

occupies  a  groove  on  the  under  side  of  the  thorax.  The  first  and  second 
joints  are  cylindrical  and  equal  in  length ;  the  last  is  longest  and  conical. 
This  apparatus  is  made  up  of  three  stiff,  pointed  setae. 

Habitat. — The  bedbug  is  common  in  old  or  carelessly  kept  houses.  Prima- 
rily it  is  an  inhabitant  of  the  woods,  and  may  be  seen  under  the  bark  on  old 
stumps.  It  insinuates  itself  in  houses  by  various  means,  and  finds  lodgment 
in  cracks  and  recesses  in  all  kinds  of  furniture.  It  studiously  avoids  light, 
and  is  seldom  seen  from  its  hiding-place  during  the  day.  It  will  not  live  on 
the  bodies  of  persons,  although  it  may  take  refuge  in  clothing  and  be  thus 
transported  from  place  to  place.  The  odor  of  the  human  body  appears  to 
attract  these  insects,  though  other  animals  are  also  subject  to  their  attacks 
(bais  and  pigeons).  Blood  is  not  drawn  by  suction,  however.  After  a 
puncture  is  made,  the  insect  receives  the  blood  by  capillary  attraction  aided 
by  the  attending  vertical  motion  of  the  several  parts  of  the  rostrum.  Those 
parts  of  the  human  body  furnished  with  odiferous  glands  appear  to  be  free 
from  their  attacks.  It  is  very  doubtful  whether,  as  has  been  said,  they  ever 
introduce  themselves  into  any  of  the  cavities  of  the  head,  especially  the 
ear,  with  its  guard  of  ceruminous  material.  The  mark  from  the  bite  is 
familiar  to  all.  The  irritation  produced  is  doubtless  due  to  the  introduction 
of  some  of  the  juices  of  the  insect  into  the  wound. 

The  bug  has  its  insect  enemies.  The  Reduvius  personatus  seeks  nearly 
the  same  habitations  with  the  bedbug,  and  when  in  search  of  prey  covers 
itself  with  dust  and  other  material,  so  that  it  is  impossible  to  recognize  it. 
It  attacks  the  bedbug  with  its  rostrum  (it  also  is  a  Hemipterous  insect)  and 
finds  it  an  easy  prey.  Ants  also  seek  and  eagerly  devour  bedbugs. 

Many  other  Hemipterous  insects  have  the  power  of  injuring  man  by  the 
prick  of  their  rostrum.  Among  the  most  notable  of  these  are  the  Prionotus 
novenarius  and  several  species  of  Notonecta  and  Nepa. 

Prionotus  novenarius  may  be  found  during  the  summer  months  on  fences, 
etc.,  in  the  country.  It  is  generally  about  one  inch  long,  and  covered  with  a 
very  fine  and  dense  cinereous  pubescence.  The  head  and  neck  are  long  and 
cylindrical ;  the  thorax  elevated  into  an  acute  serrated  ridge,  convex  from 
front  to  rear.  The  sides  of  the  abdomen  are  reflexed,  giving  that  part  of 
the  body  a  concave  appearance.  The  bug  walks  very  slowly  and  with  meas- 
ured steps,  and  when  caught  by  one  not  expert,  inserts  his  rostrum  into  the 
hand,  causing  a  feeling  of  acute  pain  which  may  last  for  some  hours,  but 
gradually  passes  away,  leaving  a  feeling  of  numbness  in  the  part. 

NOTONECTA  (Boat-fly),  Geoff. — Hemiptera.  Scutellum  distinct,  rostrum 
conical  and  articulate,  tarsi  of  two  joints  each.  The  four  anterior  feet  elbowed 
with  the  tarsi  cylindrical,  simple  and  terminated  by  two  hooks.  Antennae 
very  short  and  but  four-jointed.  The  thorax  wider  than  long.  The  hemi- 
elytra  cover  the  abdomen  above.  The  first  two  pair  of  legs  are  very  short 
and  constructed  on  the  plan  of  the  land  Hemiptera.  The  hind  are,  however, 
very  long  and  fimbriate,  acting  the  purposes  of  oars,  propelling  the  insect 
with  considerable  rapidity  under  water.  Body  somewhat  fusiform,  obtuse  in 


INSECTA.  153 

front.    The  whole  insect  is  of  a  greenish  color,  with  irregular  patches  of 
darker  hue. 

It  measures  rather  more  than  6"'  in  length. 

Habitat. — Small  streams  during  the  summer. 

In  their  larval  condition,  and  even  when  adult,  these  animals  feed  upon 
other  aquatic  insects.  The  wound  occasionally  received  upon  handling  the 
Notonecta  is  very  painful,  and  rather  large,  from  the  obtuseness  of  their 
rostrum. 

NEPA  (Water-scorpion). — Hemiptera.  Anterior  tarsi  of  one  piece,  the 
four  posterior  tarsi  of  two.  The  antennae  forficulate,  short,  and  three- 
jointed  ;  rostrum  short,  obtuse,  and  curved  beneath.  The  two  anterior  feet 
with  short  coxae,  and  the  femora  much  larger  than  the  other  parts.  Body 
straight,  elongate,  and  presents  an  elliptical  contour.  Abdomen  terminated 
by  two  slender  bristles,  which  are  employed  in  respiration. 

In  form  they  are  elongate  oval,  depressed.  Their  color  is  testaceous  or 
dark-ash.  They  vary  in  length  from  \"  to  4"  or  5".  The  larger  species  are 
tropical. 

Habitat.— Fresh  water  streams — preferring  still  water. 

The  insect  is  a  very  poor  swimmer,  preferring  to  walk  along  the  bottom  of 
streams.  It  flies  at  night  with  great  rapidity,  and  takes  wing  by  climbing 
to  the  upper  end  of  any  twig  growing  in  the  water.  The  rostrum,  as  in 
Notonecta,  is  short  and  obtuse  and  the  wound  inflicted  very  painful  but  not 
at  all  dangerous. 

APHIS.  Antennae,  properly  speaking,  longer  than  the  thorax,  composed  of 
seven  articles.  The  tarsi  are  composed  of  two  articles;  the  antennae  are  fili- 
form, or  in  the  form  of  setae,  longer  than  head,  and  composed  of  six  to 
eleven  articles.  Bodies  short,  oval,  and  soft,  and  furnished  at  the  hinder  ex- 
tremity with  two  little  tubes,  knobs,  or  pores,  from  which  exude  almost  con- 
stantly minute  drops  of  a  fluid  sweet  as  honey ;  heads  small,  beaks  long  and 
tubular ;  eyes  globular ;  upper  wings  nearly  twice  as  large  as  the  lower, 
much  longer  than  body,  nearly  triangular,  and  gradually  widened  toward  the 
extremity ;  they  are  almost  vertical  when  at  rest,  and  cover  the  body  like  a 
sharp-ridged  roof.  (Harris.) 

Measurement. — 1£'"-2"'  long. 

Habitat.— A  variety  of  plants.  A.  rosce  is  found  on  the  rose-bush  ;  A. 
brassicce,  the  cabbage.  The  irritation  excited  by  the  act  of  the  insect  se- 
curing its  food  causes  excrescences  to  grow  upon  various  parts  of  the  infected 
plant.  These  are  technically  known  as  '  galls.'  Thus  a  '  gall  case '  is  ob- 
tained from  the  Dactylium  racemosum.  The  pistachia  galls  are  derived  from 
pistachia  tree  of  Southern  Europe.  The  Chinese  galls  are  the  product  of  an 
imperfectly  known  tree. 

Coccus. — Hemiptera.  Tarsi  each  with  but  a  single  point,  with  a  single 
hook  at  end.  Male  without  rostrum,  but  possessed  of  two  wings,  which  lie 
horizontally  upon  the  body ;  abdomen  terminated  by  two  setae.  The  female 
without  wings,  and  provided  with  a  rostrum. 


OF  THE 

TJ1U7BRSIT7 


154  MEDICAL   ZOOLOGY. 

often  of  eleven  articles.  (Regne  Animal.)  These  insects  vary  very  much  in 
form  ;  some  of  them  are  oval  and  slightly  convex  scales,  and  others  have  the 
shape  of  a  muscle ;  some  are  quite  convex,  and  either  formed  like  a  boat 
turned  bottom  upwards,  or  are  kidney-shaped,  or  globular. 

Measurements. — l'"-!^'"  in  length. 

Habitat. — They  live  mostly  upon  the  bark  of  the  stems  of  plants  ;  some, 
however,  are  habitually  found  under  leaves,  and  some  on  roots.  The  supply 
for  commercial  purposes  is  received  from  Mexico.  Specimens  have  been 
seen  on  Opuntia  in  Nevada,  by  Mr.  Wm.  M.  Gabb,  and  in  Idaho  by  Lt.-Col. 
A.  W.  Bowman,  U.  S.  A. 

Species  mentioned  in  connection  with  medicine:  C.  cacti;  C.illicis;  C. 
lacca.  (Moquin-Tandon.) 

APIS. — Hymenoptera.  Neuter.  Body  nearly  cylindrical,  and  subpubescent. 
Head  transverse,  about  as  wide  as  the  thorax ;  vertex  and  face  deeply  longi- 
tudinally channeled  in  the  centre ;  the  ocelli  rather  large ;  compound  eyes 
very  pubescent;  antennae  short,  filiform,  geniculated ;  the  scape  (basal  joint) 
nearly  half  the  length  of  the  flagellum  (remaining  joints),  and  subfusiform; 
clypeus  (piece  behind  labrum)  quadrate,  convex;  labrum  transverse,  linear, 
slightly  waved  in  front;  mandibles  broad  at  apex  ;  cibarial  apparatus  short- 
ish ;  tongue  nearly  twice  the  length  of  the  labrum,  linear,  pubescent,  and 
terminating  in  a  small  knob ;  labial  palpi  not  quite  so  long  as  tongue ;  max- 
illae broad,  hastate  (triangular) ;  maxillary  palpi  extremely  short,  the  basal 
one  the  shortest.  Thorax  subglobose  ;  prothorax  inconspicuous ;  metathorax 
truncated  ;  legs  slender,  subpilose  ;  the  anterior  and  intermediate  tibiae  with 
a  spur ;  their  plantae  (under  surface  of  first  tarsal  joint)  with  a  dense  short 
close  brush  all  round  ;  the  posterior  tibiae  triangular,  glabrous  within,  extern- 
ally smooth,  shining,  and  irregularly  concave,  the  edges  fringed  longitudinally 
with  long  hair  curving  inwards,  and  forming  the  sides  of  the  corbiculum  (re- 
ceptacle), which  conveys  the  material  of  the  nest ;  the  apex  transverse  and 
pectinated  with  short  rigid  setae,  but  wholly  without  spurs ;  the  plantae  oblong, 
not  quite  as  long  as  the  tibiae,  the  sides  nearly  parallel,  the  upper  edge  fringed 
with  long,  loose  hair,  subglabrous  externally,  but  furnished  internally  with 
ten  transverse  parallel  rows  of  short  hair ;  the  remainder  of  the  tarsal 
joints  short,  the  fourth  the  shortest,  and  the  claw-joint  the  longest ;  the  claws 
short,  robust,  and  bifid.  Abdomen  retuse  (obliquely  truncate  at  base),  sub- 
cylindrical,  convex  above,  and  terminating  conically,  the  first  segment  very 
short,  the  second  the  longest,  the  ventral  segments  rigid  longitudinally  in  the 
centre. 

Female  (Queen)  head  not  so  wide  as  thorax,  in  having  the  cibarial  appa- 
ratus very  much  shorter  ;  the  mandibles  distinctly  bidentate,  the  inner  edge 
of  the  inner  tooth  stretching  obliquely  to  the  acute  inner  extremity  of  the 
broad  apex  of  the  organ ;  the  labial  palpi  as  long  as  the  tongue,  with  all  the 
joints  conterminous,  the  basal  one  slightly  acuminate,  the  second  linear, 
the  two  terminal  ones  more  slender  and  shorter,  the  pubescence  of  the  eyes 
very  much  longer  than  in  the  neuter;  the  legs  more  robust  and  less  pilose; 


INSECTA.  155 

the  posterior  tibiae  convex  externally,  without  the  lateral  fringes  of  hair,  and 
their  plantae  merely  oblong,  without  the  external  basal  auricle.  The  abdo- 
men is  also  considerably  relatively  longer,  and  has  not  the  central  ventral 
ridge. 

The  male  (Drone)  differs  from  both  in  being  considerably  more  robust  and 
more  completely  cylindrical,  and  ve*ry  much  more  densely  pubescent;  the  com- 
pound eyes  contiguous  at  the  summit,  occupying  the  whole  of  the  vertex  and 
nearly  all  the  lateral  portions  of  the  face,  extending  below  the  articulation 
of  the  mandibles,  their  pubescence  much  shorter,  but  denser  than  in  the 
other  sex ;  the  ocelli  large,  and  seated  at  the  top  of  the  central  portion  of 
the  face  in  a  close  triangle,  a  little  above  the  insertion  of  the  antennae,  and 
in  front  ot  the  conjunction  of  the  compound  eyes ;  the  antennae  are  more 
robust  and  rather  longer ;  the  cibarial  apparatus  rather  short ;  the  labial 
palpi  about  three-fourths  the  length  of  the  tongue,  and  the  joints  contermin- 
ous, the  tongue  robust ;  the  thorax  nearly  quadrate,  the  legs  nearly  naked, 
the  four  anterior  very  slender ;  the  posterior  tibiae  slightly  curved,  convex 
externally;  the  posterior  plantae  more  robust,  and  more  convex  externally 
than  their  tibiae, — they  are  regularly  oblong,  and  without  the  basal  auri- 
cles,— the  rest  of  the  joints  of  the  tarsi  are  very  short.  The  abdomen  robust, 
and  obtuse  at  its  extremity,  but  its  seventh  segment  is  concealed  beneath ; 
the  ventral  segments  concave  longitudinally.  (Shuckard.) 

A.  mellifica. — Linnaeus. 

CYNIPS  (Gall-fly). — Hymenoptera.  Antennae  13  to  14  pieces;  wings  not 
markedly  nervose;  their  palpi  short,  and  ovipositors  longer  than  abdomen. 
Head  transverse,  small ;  the  thorax  large ;  abdomen  compressed,  the  profile 
somewhat  circular  and  generally  furnished  with  a  short  pedicle.  Antennae 
inserted  upon  the  middle  of  face ;  those  of  the  $  are  ordinarily  shorter  and 
thicker  than  the  £  .  1st  joint  is  thick,  2d  short,  3d  is  larger  than  the  other 
two  and  often  scalloped  or  curved  in  the  $ .  The  upper  lip  is  very  small ; 
mandible  short,  thick,  with  extremity  armed  with  small  teeth ;  jaws  termin- 
ating in  a  membranous  lobe  (galea)  ;  maxillary  palpi  have  five  joints,  and 
the  labial  palpi  two  or  three. 

The  greater  part  of  the  thorax  is  from  the  mesothorax.  Wings  are  cellu- 
lar, the  greater  portion  being  made  up  of  cells  at  the  radial  or  cubital  mar- 
gins. The  2d  pair  leave  up  a  single  very  thick  nerve. 

The  1st  segment  of  the  abdomen  is  large,  while  the  others  are  short.  The 
superior  is  arched  and  prolonged  under  the  ventral  face.  One  segment  forms 
a  salient  point,  and  directed  posteriorly  protects  the  position  of  ovipositor. 
This  latter  is  extremely  slender  and  lodged  in  the  abdomen,  or  it  is  protected 
by  two  valves  or  two  semi-straight.  The  organ  itself  is  extremely  short  and 
composed  of  a  single  incomplete  cylinder,  which  is  lodged  in  two  slits  or 
spicules  composing  the  ovipositor  proper.  It  resembles  the  ovipositor  of 
other  Hymenoptera.  It  is  moved  by  strong  muscles,  and  is  not  seen  exter- 
nally in  a  state  of  repose. 


156  MEDICAL    ZOOLOGY. 

The  larvae  of  the  gall  insect  are  apodal.  Some  live  five  and  six  months, 
then  descend  to  earth  and  assume  the  condition  of  nymph.  Others  go  through 
all  their  changes  in  the  gall  itself. 

Species. —  C.  quercus  tindoria,  C.  kollari,  C.  rosce,  C.  longipennis,  C. 
msana,  C.  polycera,  C.  hungarica. 

POLEX  (Flea).  Hemiptera.  Mandibles  and  lingua  long,  setiform ;  maxillae 
small,  triangular,  palpi  four-jointed ;  labium  minute,  palpi  three-jointed. 
Body  compressed.  Antennae  short  with  three  joints,  the  last  large,  flat, 
serrated,  received  in  a  small  cavity,  and  covered  with  a  scale.  Max.  palpi 
with  four  joints,  porrect.  Post,  feet  saltatory.  Tarsi  with  five  joints. 

Four  small  round  plates,  situated  between  last  two  segments  of  thorax ; 
post,  pair  largest,  and  represent  rudiments  of  wings.  Eyes  two,  simple ; 
wanting  in  P.  vespertilionis.  No  marked  distinction  between  thorax  and 
abdomen. 

Development. —  $  twelve  eggs,  rounded,  whitish  color;  larvae,  grubs  with 
thirteen  joints,  last  two  hooked.  Twelve  days  as  inactive  pupae. 

P.  irritans  (Common  flea). 

P. penetrans  (chigue,  chigger,  jigger).  The  9  and  £  do  not  attack  man 
prior  to  impregnation.  After  this,  £  introduces  itself  under  the  nails  or 
between  toes  of  feet ;  causes  a  white  globular  vesicle,  by  rapid  growth  of 
larvae,  which  are  contained  in  a  sac  attached  to  abdomen  by  mother.  In 
treating  this  condition  the  small  orifice  is  gradually  dilated  and  the  objects 
removed.  Scotch  snuff  or  capsicum  then  placed  in  wound. 

PEDICULUS  (Louse). — Diptera.  Antennae  as  long  as  thorax  ;  sucker  is  an 
inarticulate  sheath,  armed  with  retractile  hooks;  eyes  simple;  abdomen 
notched  at  borders. 

P.  capitis. — Thorax  distinct,  elongate,  quadrangular,  narrower  than  ab- 
domen ;  seven  segments  notched  at  margin ;  stigmata  upon  six  ant.  segments, 
circular,  and  furnished  with  a  small  opening  in  the  middle.  Stigma  between 
first  and  second  pairs  of  feet  is  often  indistinct,  and  resembles  a  papilla. 
Color  varies,  livid  or  pale  gray,  and  is  said  to  adapt  itself  to  that  of  the 
hair ;  all  the  segments  are  blackish  on  the  margins.  In  the  human  louse, 
transverse  ridges;  feet  similar;  tarsus  one  joint, — bears  a  large  claw  on  its 
outside,  and  on  its  inside  two  straight,  thick,  horny  stumps,  and  a  large  bris- 
tle. (Esophagus  short ;  stomach  longish ;  two  caecal  appendages ;  intestine 
slightly  sigmoid, — receives  four  urinary  vessels  at  its  extremity,  and  passes 
on  into  the  pyriform  large  intestine. 

$  fewer;  last  abdominal  segment  is  prominent  and  rounded  off,  furnished 
on  its  dorsal  surface  with  a  valvular  opening,  beset  with  an  abundance  of  as- 
perities, anal  and  vaginal ;  two  pairs  testes ;  simple,  wedge-shape  penis,  base 
upwards,  apex  outwards,  opens  on  back, — chitinous. 

9  apex  caudal  not  notched  ;  two  lobes,  between  which  is  the  anal  aper- 
ture ;  two  ovaries  consist  of  five  tubes  each,  forming  two  oviducts  emptying 


ARACHNIDA.  157 

into  a  common  vagina,  into  which  two  seminal  receptacles  open ;  genital  pore 
on  ventral  surface  between  penultimate  and  last  segment.  Its  lower  surface 
forms  a  transverse  ridge.  Copulation  by  $  beneath  £  .  Eggs  pyriform,  £"'; 
in  six  days  young  escape ;  a  louse  fifteen  days  old  can  lay.  J  lays  fifty  eggs. 

Two  9  might  become  progenitors  of  10,000  lice  in  eight  weeks ;  a  single 
generation  may  furnish  2500  lice,  the  third  125,000.  (Leuwenhoek.) 

P.  vestimenti. — Body  louse  pretty  near  preceding.  Head  exserted,  elon- 
gated in  second  joint ;  antennae  elongated ;  thorax  divided  into  segments ; 
dirty  white,  blacker  on  margins ;  principal  distinctions  between  body  and 
head  louse  pertaining  to  size. 

Phthirius .pubis.  —  Fiddle-shaped  head;  prominent  eyes;  antennae  five 
joints. 

Habitat. — Pubis,  hairs  of  breast,  eyebrows,  eyelashes. 

Schultz  regards  lice  beneficial ;  couriers  cherish  them,  to  place  them  under 
the  prepuce  of  their  horses  to  excite  animation. 

(Pyrethrum  caucaseum,  Persian  insect  powder.) 


ABAOHNIDA, 

SARCOPTES.  Body  circular,  indented  towards  centre  and  obtuse  poste- 
riorly, soft,  shiny,  slightly  transparent,  of  a  whitish  color.  Dorsal  surface 
convex,  ventral  less  so.  Margin  slightly  undulating,  and  the  surface  of  ab- 
domen is  marked  by  more  or  less  parallel,  irregular,  but  curved  lines  or 
ridges.  Rostrum  anterior  and  straight,  somewhat  oval,  obtuse,  two  setae  at 
base.  Limbs  eight  in  number,  two  pairs  in  front,  and  two  placed  farther 
back.  Limbs  short,  conical,  distinctly  jointed  and  furnished  with  hair-like 
processes.  The  two  anterior  pair  arise  from  the  thorax ;  they  have  thighs 
divergent ;  the  feet  terminate  in  slender,  straight,  rigid,  setae,  tubular  segment 
provided  at  its  extremity  with  a  sucker.  The  four  posterior  feet  pertain  to 
the  abdomen ;  they  terminate  in  a  long,  curved,  pointed  thread,  without 
sucker.  The  body  of  the  insect  has  a  few  hair-like  processes  scattered  here 
and  there,  and  on  its  dorsal  surface  are  three  kinds  of  horny  appendages  or 
spires  ;  the  first  fourteen  in  number  are  arranged  symmetrically  on  its  central 
and  posterior  parts,  of  a  conical  form,  are  traversed  by  a  canal,  and  furnished 
with  a  dilatation  or  basal  follicle ;  the  second  are  smaller,  and  placed  near 
the  first ;  the  third  are  still  more  minute ;  they  are  arranged  in  concentric 
lines,  have  no  canal,  and  resemble  conical-pointed  tubercles. 

The  parts  about  the  mouth  are  surrounded  at  their  commencement  by  a 
thin  sinuous  margin,  portions  of  which  extend  as  far  as  the  organs  them- 
selves. These  are  as  follows :  1st.  A  pair  of  strong  mandibles,  carrying 
toward  their  extremity  and  on  their  upper  side  a  small  movable  hook ;  this 


158  MEDICAL    ZOOLOGY. 

is  pointed,  somewhat  curved,  and  when  not  in  use  is  received  into  an  oblique 
groove,  with  irregular  dentated  margins,  situated  on  the  opposite  side  of  the 
prolonged  portion  of  the  organ.  2d.  The  maxillae, — these  are  small,  nar- 
row, and  curved  from  without  inwards.  Their  base  is  articulated  to  a  small 
square  piece,  the  chin.  Their  palpi  are  large  pieces  supported  by  the  max- 
illae, curve-pointed;  and  composed  of  three  unequal  joints.  The  terminal 
joint,  which  is  the  smallest,  presents  externally  a  single  long  hair,  while 
the  middle  joint  has  two.  3d.  The  labium  ;  this  is  nearly  triangular  and 
somewhat  pointed.  Toward  its  base  and  on  both  sides  there  is  very  long 
hair.  4th.  The  tongue ;  this  is  lancet-shaped,  and  placed  in  median  line. 

The  resophagus  is  long  and  straight.  Arrived  at  the  anterior  third  of  the 
body,  this  canal  terminates  in  an  oblique  reniform  stomach,  transparent  and 
difficult  to  observe.  Intestine  short  and  slightly  undulating;  it  contains  a 
number  of  brown  granules,  which  occasionally  accumulate  toward  its  term- 
ination. Respiration  effected  in  skin.  Sexes  on  separate  individuals.  Male 
smaller,  more  oblong,  flatter,  of  a  darker  color,  and  more  active ;  the  ros- 
trum is  proportionately  smaller  and  less  triangular ;  they  have  not  so  many 
horny  appendages  on  the  dorsal  surface.  The  anterior  feet  extend  beyond 
the  anterior  third  of  the  body,  reaching  nearly  to  its  centre ;  the  posterior 
limbs  are  not  so  wide  apart ;  the  third  pair  of  feet  are  furnished  with  longer 
hairs  ;  lastly,  the  fourth  pair  are  much  shorter,  and  have  ambulacra  furnished 
with  a  sucker.  The  genital  apparatus  is  placed  toward  the  middle  of  the 
body,  near  the  third  pair  of  limbs.  The  testicles  are  simple,  the  vas  deferens 
with  two  median  glandular  bodies  attached ;  the  penis  of  tolerable  length, 
contained  within  a  groove  ;  genital  pore  a  little  in  front  of  the  posterior 
margin  of  body.  Males  fewer  in  number  than  the  females,  the  proportion 
being  about  one  of  the  former  to  ten  of  the  latter. 

With  the  female  the  genital  pore  is  situated  on  ventral  surface  at  a  short 
distance  from  the  sternal  plates.  It  communicates  with  a  granular  body 
hardly  discernible  except  at  the  period  of  reproduction.  The  female  is  ovip- 
arous, laying  one  egg  at  a  time.  The  young  Sarcoptes  are  active,  and  pos- 
sess but  six  legs.  (Moquin-Tandon.) 

S.  scabei. 

DEMODEX.  D.folliculorum. — Body  grayish  white,  semi-transparent ;  head 
compounded  with  thorax  (cephalothorax)  ;  rostrum  small,  two  lateral  palpi 
with  sucker  placed  between  them;  last  terminal  joint  seven  palpi  notched; 
lip  two  slender  pieces  ;  abdomen  vermiform  ;  feet  of  three  joints,  last  provided 
with  three  hooks, 'one  long,  two  short ;  young  animal  with  six  feet ;  eggs  ellip- 
tical ;  9  oviparous — three  varieties  seen  in  relation  to  development  of  abdo- 
men, either  shorter  than,  as  long  as,  or  longer  than  -cephalothorax. 

Habitat. — Sebaceous  follicles  of  face,  nose,  and  auditory  canal. 

Measurements. — T  *-</'  to  T§ V"  in  length,  and  from  yi/"  to  T£<y'"  in  breadth. 

Simon  and  Henle  found  them  in  ext.  aud.  meatus.  Found  present  in  one 
in  ten  individuals.  Greasy  freckled  faces  more  liable.  Live  in  colonies, 
fifteen  to  eighteen  being  found  in  a  single  follicle. 


MYBIAPODA. — ANNELIDA.  159 


MYRIAPODA. 

SCOLOPENDRA.  The  mouth  of  the  Scolopendra  is  composed  of  a  square- 
shaped  lip,  of  two  mandibles,  of  two  palpi,  or  small  foot  jaws,  and  of  a 
second  lip  formed  by  another  pair  of  dilated  foot  jaws,  which  are  joined  to- 
gether at  their  commencement.  The  latter  are  the  organs  which  constitute 
the  formidable  weapons  of  the  animal.  The  poison  gland  is  lodged  in  the 
interior  of  these  organs  towards  the  base.  It  is  oval,  oblong,  and  provided 
with  a  long,  narrow  excretory  canal.  The  forceps  terminate  in  a  strong, 
pointed,  movable  hook ;  the  claw  is  provided  with  a  small  oblong  aperture 
on  its  under  surface,  which  allows  of  the  exit  of  the  poison.  (Moquin-Tan- 
don.) 

S.  scopoliana,  Europe ;  S.  heros,  Texas. 


ANNELIDA, 

HIRUDO  (Leech). — Sub-class  Discophora.     Order  Hirudinea. 

Characters. — Elongate-articulates,  with  flattened  bodies,  narrowed  ante- 
riorly, broadened  posteriorly,  composed  of  ninety-five  equal  and  distinct 
rings,  which  project  at  the  sides.  The  dorsal  surface  is  marked  with  six 
parallel  longitudinal  bands  of  a  reddish  or  brownish  hue,  spotted  with  black, 
continuous  or  intercepted,  and  sometimes  reduced  to  mere  points.  The  ven- 
tral surface  is  either  of  a  uniform  color  or  spotted  with  black,  and  bordered 
on  each  side  by  a  straight  or  undulating  line  of  the  same  color.  The  ante- 
rior extremity  is  provided  with  an  oral  sucker,  having  an  acuminate  upper 
lip.  The  posterior  extremity  bears  a  round,  obliquely  placed  sucker,  at  the 
base  and  upper  part  of  which  is  the  anus.  Within  the  mouth  are  three  pairs 
of  jaws,  furnished  with  minute  teeth.  The  eyes  are  ten  in  number,  small  • 
they  are  placed  on  the  upper  lip,  where  they  form  a  curved  line,  the  six  an- 
terior being  the  largest.  Leeches  are  androgynous.  The  sexual  orifices  are 
placed  on  the  anterior  third  of  the  belly;  the  male  orifice  between  the 
twenty-seventh  and  twenty-eighth  ring,  and  the  female  five  rings  farther 
back.  The  first  is  a  minute  pore  surrounded  by  a  thickened  margin ;  the 
second,  a  small  transverse  slit. 

H.  medicinalis  (Gray  leech),  Linn.  Body  olive  green  mixed  with  gray. 
Six  rusty  red  longitudinal  stripes  mark  the  dorsal  surface.  The  sides  are 
olive  green  ;  the  belly  is  spotted  with  black. 

Habitat. — Northern  Europe  and  certain  parts  of  northern  Africa. 

H.  officinalis  (Green  leech).  Body  of  a  clear  olive  or  green  color.  Dor- 
sal surface  distinguished  by  six  rusty  red  longitudinal  bands,  generally  con- 


160  MEDICAL    ZOOLOGY. 

tinuous.  The  margins  are  of  an  olive  color  both  on  the  back  and  belly. 
This  species  closely  resembles  the  above,  and  is  found  in  the  same  localities. 

H.  decora  (American  leech),  Say. 

Body  livid,  with  a  dorsal  series  of  twenty-two  small  red  dots,  and  a  lateral 
series  of  the  same  number  of  black  dots  of  a  similar  size  ;  a  transverse  line 
of  ocular  points  in  -close  order  before  ;  on  each  side  of  which,  and  at  a  short 
distance  from  them  and  from  each  other,  are  two  points  of  the  same  kind  ; 
hence  the  fulvous  with  a  few  black  spots. 

Anatomy. — The  jaws  of  the  leech  are  three  in  number,  placed  longitudin- 
ally :  one  superior  and  median,  two  others  inferior  or  lateral.  Each  jaw  is 
semicircular,  thin,  smooth,  and  moderately  strong.  The  free  convex  surface 
is  furnished  with  forty-six  to  eighty-three  teeth-like  chevron-shaped  processes, 
arranged  parallel  to  each  other  and  placed  across  the  cutting  edge  of  the 
jaw,  having  the  angle  turned  toward  the  axis  of  the  mouth.  (Moquin- 
Tandon.)  The  ventral  ganglia  of  the  nervous  system  are  much  fewer  than 
the  segments  of  the  body,  and  are  bound  together  by  two  contiguous  cords. 
The  first  and  last  of  these  ganglia  are  remarkable  for  their  size.  The  first 
sends  filaments  to  the  lips,  the  second  to  the  caudal  sucker.  Each  eye-speck 
composed  of  a  transparent  cylindrical  body,  a  little  attenuated  and  rounded 
at  its  inferior  extremity,  while  the  opposite  one  causes  the  skin  to  bulge  out 
like  a  cornea.  Its  remaining  portion  is  enveloped  with  a  layer  of  black  pig- 
ment. The  intestinal  canal  varies  very  much,  especially  as  to  the  number 
and  volume  of  its  appended  caeca.  Its  very  narrow  anal  opening  is  upon 
the  back  above  the  pedal  sucker.  The  blood-vessel  system  resembles  in  plan 
that  of  other  Annelida.  Beside  two  median  vessels,  there  are  distinguished 
two  lateral  ones,  which  intercommunicate  by  very  numerous  transverse  ves- 
sels. From  the  contractions  of  these  vessels,  the  blood  is  driven  sometimes 
forward  and  sometimes  backward,  and  oscillates  from  side  to  side  through 
the  transverse  canals.  With  the  Hirudinea  the  two  sexes  are  always  united 
in  the  same  individual.  The  sexual  organs  consist  of  testicles,  vasa  defer- 
entia,  and  vesiculae  seminales ;  then  ovaries,  oviducts,  and  the  male  and 
female  copulatory  organs.  The  latter  are  upon  the  ventral  surface  of  the 
anterior  part  of  the  body  and  behind  the  male  organs,  so  that  two  individuals, 
by  placing  together  their  anterior  ventral  surfaces  in  an  inverse  position,  can 
be  mutually  impregnated. 


ENTOZOA.  161 


ENTOZOA  (Internal  Parasites), 

Parasites  may  be  either  vegetable  or  animal. 

Among  the  former  may  be  mentioned,  Achorion  schonleini,  Oidium  albi- 
cans,  Sarcma  ventriculi,  Penicillium  glaucum.    Animal  parasites  chiefly 
belong  to  the  articulate  type.     Divided  into  Entozoa  and  Ectozoa. 
Ectozoa,  see  pp.  151,  156, 157,  158. 
Entozoa  divided  into — 

(  Nematoidea. 
Helminths.     -\  Trematoda. 
(^  Cestoda. 

(  Parasitic  Infusoria. 
Protozoons.    -\  Psorospermiae. 
(^  Gregarinidae. 

NEMATOIDEA.  Body  elastic,  hollow,  sub-cylindrical.  Alimentary  canal 
simple.  Head  but  slightly  protractile.  (Diesing.)  A  fine  chitinous  cuticle 
invests  the  body  to  be  shed  twice  a  year.  A  water-vascular  system  exists  in 
the  form  of  two  long  tubes,  ending  caecally  at  each  end  and  traversing  each 
lateral  thickening  of  the  dermis.  Toward  the  anterior  end  of  the  body 
each  tube  gives  off  a  small  branch,  and  these  two  branches  uniting  together 
open  externally  by  a  small  pore.  The  nervous  system  may  be  said  to  con- 
sist of  an  oesophageal  ring,  with  three  ganglia — two  lateral  and  one  ventral, 
the  latter  being  far  the  largest.  Nervous  fibres  are  continued  backwards 
along  the  ventral  side  of  the  body  to  the  anus ;  and  several  nervous  fibres 
are  said  to  run  forward  from  the  cesophageal  ring.  No  sensory  organs  have 
been  discovered  besides  the  papillae  of  the  mouth,  except  in  free  forms, 
which  are  provided  with  eyespots.  The  alimentary  canal  is  of  variable  form. 
The  Nematoidea  were  supposed  to  be  all  dioecious  by  Schneider ;  but  the 
Anguillidae  inhabiting  putrefying  snails  have  an  ova-testis,  and  the  same 
structure  has  been  said  to  exist  in  an  Ascaris.  Males  smaller  than  females  ; 
each  has  a  long  vas  deferens  opening  below,  in  the  front  wall  of  a  sort  of 
cloaca,  while  its  caecal  upper  end  furnishes  sperm  cells,  the  complete  devel- 
opment of  the  spermatozoa  only  taking  place  inside  the  female.  The  oviduct 
of  the  latter  is  similar  in  form  to  the  male  tube  just  mentioned,  and  ova  are 
secreted  at  its  caecal  upper  portion.  (Huxley.) 

Trichina. 


11 


162  MEDICAL    ZOOLOGY. 

T.  spiralis.  Body  rounded  and  filiform  ;  usually  slightly  bent  upon  itself, 
rather  thicker  behind  than  in  front,  especially  in  the  males;  head  narrow, 
finely  pointed,  unarmed,  with  a  simple,  central,  minute  oral  aperture.  Male 
possesses  a  bi-lobed  caudal  appendage,  the  anal  aperture  situated  between  its 
lobes ;  penis,  consisting  of  a  single  spicule,  cleft  above  to  assume  a  Y-shaped 
outline.  Female  stouter  than  male,  bluntly  rounded  posteriorly ;  genital  pore 
at  anterior  fifth  of  body. 

Measurements. — Male,  Ty  long ;  female,  £". 

Habitat. — Intestine  of  man  and  hog. 

Development. — The  mature  female  inhabiting  the  intestine,  after  producing 
active  young,  dies  and  is  removed  with  the  ejecta.  But  the  embryos  remain 
within  the  host,  very  soon  to  penetrate  the  walls  of  its  intestine.  After 
assuming  the  desired  position  among  the  tissues  they  become  encapsuled 
and  remain  quiescent.  When  a  portion  of  flesh  thus  inhabited  is  consumed 
by  another  animal  the  larvae  again  become  active  within  its  alimentary 
canal,  and  soon  take  on  the  sexual  form.  Coition  now  occurring,  the  female 
brings  forth  broods  of  larvae  as  before.  The  conditions  attendant  upon  the 
passage  of  large  numbers  of  larvae  from  the  intestine  to  the  surrounding 
tissues  constitutes  the  disease  Trichiniasis. 

The  most  conspicuous  instances  of  the  disorder  are  seen  when  the  infected 
flesh  of  the  hog  is  eaten,  either  raw  or  imperfectly  cooked,  by  man. 

Strongylus.  Body  subcylindrical,  rarely  prismatic  ;  attenuated  at  either 
end.  Head  naked,  continuous  with  the  body ;  rarely  alate.  Mouth  term- 
inal, orbicular  limb  not  horny,  naked  or  papillose.  Caudal  extremity  of 
male  with  terminal  entire  bursa,  truncate ;  with  one  or  more  radiated  setae. 
Penis  filiform,  contained  within  a  bi-partite  sheath.  Genital  pore  of  female 
placed  anteriorly,  rarely  posteriorly.  (Diesing.) 

S.  bronchialis,  Cobbold.  Caudal  appendage  with  a  bi-lobed  membranous 
semi-bell-shaped  bursa  (supposed  to  be  an  accessory  organ  of  copulation) 
which  surrounds  the  cloacal  outlet.  Penis  a  double  spiculum  lying  in  cloaca. 
Female,  tail  sharply  pointed,  anus  little  in  front  or  above  the  narrow  part ; 
body  filiform,  pale  yellow  color,  ^  of  an  inch  broad;  viviparous. 

Measurements.— Male,  6'"  long,  -fa"  wide;  female,  1"  long,  5y  wide. 

Dis.  by  Treutler,  Germany,  1791,  in  the  bronchial  glands  of  an  emaciated 
subject.  Confined  to  the  air-passages. 

Tricocephalus. — Body  subcylindrical,  rather  thick.  Male  mostly  spiral ; 
female  straightish.  Neck  very  long,  gradually  thickening  posteriorly.  Head 
scarcely  distinct.  Caudal  bursa  rarely  unarmed,  with  a  filiform  penis  with- 
drawn within  a  retractile  sheath.  End  of  tail  of  female  straight  and  some- 
what obtuse  ;  genital  aperture  at  base  of  neck.  (Diesiug.) 

T.dispar,  Rudolphi. — Male,  long;  neck,  two-thirds  length  of  body;  skin 
with  wart-like  appendages  on  one  side  only;  tail  curved,  emitting  at  extrem- 


ENTOZOA.  163 

ity  a  short  tubular  penis  ;  sheath  armed  with  minute  retroverted  spines ;  tail 
straight  and  bluntly  pointed. 

Measurement. — Male.  !£"'  long;  female,  2'" long.     Eggs  ?|¥"  to  f^". 

Habitat. — Head  of  large  intestine. 

Ascaris. — Body  subcylindrical,  subequal  at  either  end,  rarely  armed.  Head 
subconical,  continuous  with  body.  Mouth  terminal  trilabiate,  when  closed 
assuming  the  form  of  a  triangle.  Caudal  extremity  naked  or  winged.  Penis 
filiform,  enclosed  in  a  bipartite  sheath  with  linear  branches,  sometimes  very 
long.  Genital  pore  of  the  female  in  front  or  posterior  part  of  the  body. 
Rarely  viviparous.  (Diesing.) 

A.  lumbricoides,  Linnaeus. — Body  smooth,  fusiform  and  elastic,  marked 
by  numerous  fine  transverse  rings,  and  attenuated  gradually  toward  either 
extremity,  the  anterior  terminating  in  a  much-produced  tripapillated  mouth, 
the  posterior  in  a  bluntly  pointed  tail ;  female  much  broader  than  the  male, 
having  a  diameter  of  \  of  an  inch  and  a  circumference  of  f '";  male  repro- 
ductive organs  furnished  with  a  double  speculum  or  penis,  extremity  of  body 
arcuate;  female  genital  pore  at  lower  part  of  the  anterior  half  of  the  body. 
Measurements. —  £  from  4  "-6"  long;  $  10"-14"  long.  (Cobbold.)  Intes- 
tine terminates  in  a  cloacal  cavity  which  opens  by  a  transverse  slit  at  a  short 
distance  from  the  end  of  body.  Skin  of  two  layers:  external,  chitinous;  in- 
ternal, granular.  Spermatic  tube  3' long  in  most  specimens;  oviducts  4'. 
Gullet  long,  somewhat  triangular,  with  thickened  walls  ;  very  narrow  at  its 
commencement,  it  gradually  increases  in  size,  and  is  then  suddenly  con- 
stricted. The  stomach  consists  of  two  globular  dilatations ;  its  walls  are 
thinner  than  those  of  the  ossophagus.  The  intestine  is  straight,  and  presents 
some  slight  bendings  ;  it  becomes  narrower  toward  the  vent.  The  canal  ap- 
pears to  be  surrounded  by  white  vesicles  suspended  in  the  cavity  of  the  body. 
The  anus  is  near  the  posterior  extremity  of  the  animal,  and  has  the  form  of 
a  transverse  opening.  The  nervous  system  composed  of  two  white  cords 
running  along  the  sides  of  the  body ;  no  ganglia  apparent.  The  testicles 
and  spermatic  cords  are  filiform,  and  surround  the  alimentary  canal.  Vagina 
narrow,  uterus  short,  provided  with  long  flexible  horns.  These  become  con- 
tinuous with  the  ovaries,  which  are  long,  and  twisted  upon  themselves 
around  the  alimentary  canal. 

Development  imperfectly  known.  Eggs  are  deposited  in  water.  The  em- 
bryo subsists  for  a  long  time  active  within  the  egg  capsule.  (Moquin-Tan- 
don.) 

Habitat. — Small  intestine. 

A.  mystax,  Rudolphi. — Moderate  size ;  alaeform  appendages,  one  on  either 
side  of  head ;  mouth  trilobate.  Male  2%'"  long ;  tail  arcuate  ;  body  coiled ; 
spicules  2-5y  "  long.  Female  4  inches  long ;  less  coiled.  Eggs  measure 

si/'- 
Habitat.— 


164  MEDICAL    ZOOLOGY. 

Oxyuris. — Body  subcylindrical,  rather  thick;  caudal  extremity  acute; 
head  continuous  with  the  body  ;  mouth  terminal,  naked,  or  papillose  ;  caudal 
extremity  of  the  male  with  a  thorn-like  process ;  penis  filiform,  enclosed 
within  a  tubular  sheath  ;  female  awl-shaped,  with  the  genital  pore  at  the  an- 
terior part  of  the  body.  Oviparous.  (Diesing.) 

0.  vermicularis,  Bremser. — Male  :  caudal  extremity  obtusely  pointed  ; 
head  truncated;  mouth  with  three  papillae;  resophagus  triangular;  penis 
single,  very  small.  Female  :  tail  long,  tapering,  terminating  in  three  points. 
Eggs  oblong,  asymmetrical,  y^"  in  length,  ^ff"  in  diameter.  The  water 
vascular  system  composed  of  four  vessels — one  dorsal,  one  ventral,  and  one 
on  either  side. 

Measurements. — Male,  £"  long;  female,  £-£"  long. 

(Esophagus  with  thick  muscular  walls,  dilates  into  a  kind  of  crop  at  its 
junction  with  the  stomach ;  the  latter  is  short  and  globular.  The  com- 
mencement of  the  intestine  is  enlarged,  so  that  the  alimentary  canal  has  the 
appearance  of  three  stomachal  dilatations.  The  intestine  is  nearly  straight, 
uns  in  the  length  of  the  animal,  and  preserves  a  uniform  diameter  up  to  the 
rectum.  It  becomes  enlarged  at  the  posterior  part  of  the  body,  forming  a 
short  rectum,  to  again  gradually  narrow  like  the  tail  of  which  it  fills  the 
cone.  The  anus,  placed  at  the  middle  part  of  the  base  of  the  tail,  is  a  trans- 
verse slit.  Development  not  known. 

Habitat. — Large  intestine. 

Sclerostoma. — Body  subcylindrical,  attenuate  at  either  end ;  head  sub- 
globose  ;  mouth  terminal,  margin  subcorneous,  toothed  or  papillose.  Male 
caudal  bursa  entire  or  lobed,  multiradiate ;  penis  enclosed  in  a  bipartite 
sheath.  Female  straight ;  genital  pore  either  in  anterior  or  posterior  part 
of  body.  (Diesing.) 

S.  duodenale,  Cobbold. — The  oval  papillae  four  in  number  asymmetrically 
arranged,  uneven,  horny  (probably  chitinous),  conical  converging ;  head 
slightly  pointed  ;  tail  blunt,  partially  inflexed  ;  bursa  cup-shaped,  supported 
by  eleven  chitinous  rays — ten  simple,  odd  one  bifurcated  at  summit. 

Female. — Tail  sharp,  conical;  genital  orifice  (?) ;  oviparous;  eggs  (?). 
Females  more  numerous  than  the  males. 

Measurements. — Male,  £"  long ;  female,  £"  long. 

Dracunculus. 


D.  medinensis  (Guinea-worm),  Cobbold. 

Male  unknown.     Body  terminating  in  a  more  or  less  curved,  reversed 
mucronate  tail ;  head  somewhat  truncate  or  flatly  convex,  with  a  simple 


ENTOZOA,  165 

mouth  surrounded  by  four  papillae  ;  viviparous.  The  young  almost  fill  the 
cavity  of  body.  No  anus.  Cavity  of  body  chiefly  occupied  by  uterus,  intes- 
tine being  inconspicuous  between  it  and  integument. 

Confined  to  old  world — tropics  of  Asia  and  Africa. 

Measurements. —  I'  to  2'  long;  jls"  thick. 

The  animal  is  parasitic  only  in  the  adult  condition.  The  young  exist  in 
fresh  water  pools  and  mud  of  marshy  districts.  From  such  localities  they 
gain  access  to  the  subcutaneous  and  intermuscular  cellular  tissues  of  man, 
dogs,  and  horses,  most  probably  by  penetrating  the  ducts  of  the  sweat 
glands.  The  female  thus  lodged  grows  rapidly  and  produces  large  numbers 
of  living  y9ung,  which  subsequently  escape  to  pass  the  embryonic  stage  in 
or  about  water,  as  already  stated. 

Eustrongylus.  Body  subcylindrical,  conspicuously  attenuate  at  either 
end.  Head  continuous  with  body.  Mouth  terminal,  papillose.  Bursa  of 
male  entire,  neither  radiate  or  furnished  with  appendages.  Penis  filiform, 
long,  without  sheath.  Genital  pore  of  female  placed  anteriorly  or  pos- 
teriorly. 

E.  gigas,  Diesing. — Male.  Body  cylindrical,  and  more  or  less  deeply 
tinged  with  red ;  head  obtuse  and  furnished  with  a  simple  oral,  surrounded 
by  six  papilliform,  chitinous  nodules  ;  caudal  extremity  displaying  a  simple 
round  cup-shaped  bursa,  devoid  of  any  radiating  appendages ;  penis  con- 
sisting of  a  single  spiculum.  Female.  Tail  bluntly  pointed,  and  pierced  by 
the  anal  aperture ;  vaginal  orifice  situated  on  the  ventral  aspect,  at  a  short 
distance  below  the  so-called  head ;  mode  of  reproduction  probably  vivipa- 
rous. Eggs  broadly  oval. 

Measurements. — Male,  10"  to  14"  long;  3'"  wide.  Female,  3'  long;  6'" 
wide. 

Habitat.— Kidney. 

TREMATODA  (Flukes),  Rudolphi. — Animals  solitary,  for  the  most  part  her- 
maphroditic, rarely  unisexual,  and  commonly  furnished  with  median  or  lat- 
eral suctorial  pores.  Alimentary  canal  forkedly  divided  or  ramose,  very 
rarely  simple.  Generation  rarely  direct — alternate  generation  the  rule. 
(Klichenmeister.) 

Fasciola. 


F.  hepatica,  Linn. — Body  flat,  anterior  end  abruptly  constricted,  produced, 
rounded  and  pointed,  forming  so-called  head  and  neck ;  posterior  extremity 


166  MEDICAL   ZOOLOGY. 

less  acuminate,  sometimes  rounded,  or  even  slightly  truncated ;  margins 
smooth,  occasionally  a  little  undulate,  especially  toward  the  upper  part;  oral 
sucker  terminal,  oral  rather  smaller  than  the  ventral  (acetabulum),  which  is 
placed  immediately  below  the  root  of  the  neck;  reproductive  orifice  in  the 
middle  line,  a  little  above  the  lower  sucker ;  intromitteut  organ  usually  pro- 
truded and  spirally  curved ;  a  central,  light-colored  space,  extending  two- 
thirds  of  the  body  from  above  downward,  marks  the  region  of  the  internal 
female  reproductive  organs,  being  bordered  on  either  side  and  below  by  a 
continuous  dark  band,  indicating  the  position  of  the  so-called  yolk-forming 
organs;  a  small  brown  colored,  rosette-figure,  placed  directly  below  the 
ventral  acetabulum,  shows  the  limits  of  the  uterine  duct ;  a  series  of  dark 
lines,  branching  downward  and  outward  on  either  side,  marks  the  position 
of  the  digestive  organs.  General  color  of  body  pale  brownish  yellow  with  a 
slight  rose  tint.  (Cobbold.) 

Measurements. — 8-14'"  long;  3£-6'"  wide.  (Kiichemneister.) 

Anatomy. — Mouth  at  apical  or  lower  part  of  the  cup-shaped  cavity  of 
anterior  sucker.  (Esophagus  divides  into  two  primary  intestinal  divisions, 
the  point  of  bifurcation  being  situated  immediately  above  location  of  ext. 
reproductive  orifices.  These  divisions  pass  down  on  either  side  to  terminate 
at  caudal  extremity,  giving  off  from  the  side  a  number  of  branches  dicoto- 
mously  dividing.  The  terminal  branches  are  of  nearly  the  same  diameter  as 
those  which  are  first  given  off.  Water  vascular  system  a  central  long  trunk, 
extending  backward  from  the  upper  third  of  the  body  to  the  tail,  where  it 
terminates  in  a  foramen.  This  central  tube  divides  into  three  branches, 
which  again  more  or  less  subdivide,  anastomosing  among  themselves.  The 
tubes  during  life  are  filled  with  a  watery  fluid,  containing  a  number  of  small 
non-nucleated  corpuscles,  which  are  highly  refractile.  (Huxley.) 

The  Fasciola  is  hermaphroditic.  Testes,  one  on  either  side,  formed  of  a 
multitude  of  vermiform  tubes,  occupying  one-half  of  the  interior  of  the  ani- 
mal. The  two  vasa  deferentia  converge  and  unite  in  a  single  tube  widened 
toward  its  outlet  (receptalium  seminis),  finally  terminating  in  a  large  spiral 
penis.  This  latter  organ,  in  a  state  of  rest,  lies  within  a  distinct  sheath,  and  is 
covered  with  a  fold  of  integument,  furnished  with  a  number  of  spines.  Sin- 
gle ovary  situated  in  median  line  at  anterior  third  of  body;  emptying  into  it 
upon  either  side  are  the  ducts  of  the  yolk-bearing  glands, — two  large  masses, 
placed  one  on  either  side  of  body,  and  partially  enclosing  the  testis.  The 
oviduct  is  short,  uterine  expanse  of  tube  abrupt,  convoluted,  terminating  in 
vaginal  pore  directly  behind  and  on  a  line  with  that  for  the  male  organ ; 
oviparous. 

Habitat. — In  bile  duct  and  gall  bladder  of  a  number  of  mammals ;  rare  in 
the  human  subject. 

Distoma.  Body  depressed  or  slender.  Head  continuous  or  same  as  the 
neck.  Mouth  terminal  or  anterior,  frequently  acetabuliform.  Genital  pores 


ENTOZOA.  167 

approximate.  Acetabulura  single,  ventral,  sessile  or  pedicellate.  Anus  at 
termination  of  caudal  extremity  or  placed  dorsally.  (Diesing.) 

D.  lanceolatum,  Mehlis.  Lancet-shaped,  very  flat,  tolerably  transparent, 
and  of  a  whitish  color.  The  oral  sucker  is  proportionally  larger  than  in 
preceding  species  and  about  the  same  size  as  the  ventral  sucker ;  they  are 
both  circular.  Intestine  straight,  dioecious,  unbranched ;  penis  not  spiral. 
(Moquin-Tandon.)  The  testes  form  two  lobed  organs,  placed  one  in  front  of 
the  other  in  the  middle  line  of  the  body,  and  directly  below  the  ventral 
sucker;  the  uterine  canal  is  long,  folded,  occupying  the  central  and  hinder 
parts  of  the  body.  The  yolk  glands  cover  a  small  space  near  lateral  margin 
of  animal.  The  opening  for  water  vascular  system  is  terminal ;  it  com- 
nmnicates  with  a  contractile  vesicle,  which  passes  upward,  early  dividing 
into  two  branches,  which  extend  as  far  as  the  base  of  oesophagus  to  retrace 
their  course  a  considerable  distance  backward.  (Cobbold.) 

Habitat. — In  the  bile  passages  and  upper  portion  of  small  intestines  of 
several  mammals;  rare  in  man.  Has  been  detected  in  sole  of  foot  and 
behind  ear. 

Measurement. — 2-6'"  long;  1-2"'  wide. 

D.  opthalmobium,  Diesing.  Body  lanceolate,  oval  form.  Suckers  circular; 
posterior  farther  from  cephalic  extremity  than  in  the  other  species,  being 
nearly  in  the  centre  of  the  body.  (Moquin-Tandon.)  Intestine  bifurcated. 
as  in  D.  lanceolatum. 

Measurements. — \-\'"  long ;  £"'  wide.  (Diesing.) 

Habitat. — Four  species  found  by  Gescheidt  between  the  eye  and  its  cap- 
sule in  a  child  five  months  old.  Von  Ammon  found  eight  in  the  same  position, 

D.  crassum,  Busk.  Pointed  in  front,  rounded  posteriorly ;  testes  form 
two  bulky,  lobed  organs,  situated  below  ventral  acetabulum.  The  uterine 
folds  occupy  only  the  front  part  of  the  body,  the  margins  of  which  also  dis- 
play two  yolk  glands,  one  on  either  side  of  the  intestinal  tube ;  water  vas- 
cular duct  rudimentary.  Habitat  not  given.  Measurements. — I"6"'to3' 
long;  8'"  wide. 

D.  heteropliyes,  Von  Siebold.  Body  pyriform;  obtusely  rounded  behind; 
body  compressed,  armed  with  minute  spines ;  hinder  sucker  much  larger 
than  anterior;  oesophagus  long;  intestinal  tube  simple,  gradually  widening 
below  and  terminating  near  posterior  margin;  supernumerary  sucker  in 
neighborhood  of  reproductive  orifices  ;  eggs  red. 

Measurements. — £-f"  long  ;  \'"  wide. 

Habitat. — Egypt ;  in  small  intestine  of  man. 

Bilharzia. 

B.  hcematobia,  Cobbold.  £  Cylindrical,  vermiform,  6"'  long ;  9  longer, 
narrower,  10'"  long;  $  tuberculated  and  furnished  with  ngyncecophoric  canal 
in  which  the  female  is  lodged  in  copulation.  Intestinal  canals  reunite,  after 
a  short  separation,  to  form  a  broad,  central,  spirally  twisted  tube  extending 
down  the  middle  of  the  body ;  yolk-  and  oviducts  uniting  to  form  a  single 


168  MEDICAL   ZOOLOGY. 

canal,  which  is  expanded  at  its  lower  portion,  finally  to  open  near  the  inferior 
margin  of  the  ventral  sucker ;  eggs  pointed  at  one  end.  (Cobbold.) 

Habitat. — Egypt:  man  and  monkey.  Found  in  the  blood-vessels;  the 
eggs  may  act  as  thrombi,  yet  no  pyemic  symptoms  are  seen. 

Tetrastoma.     T.  renale,  Delia  Chiaje.    This  imperfectly  known  parasite 
possesses  an  oval  flattened  body,  5"'  long,  having  4  suckers  at  caudal  end. 
Habitat. — Kidney ;  very  rare ;  only  one  case  recorded. 

Hexathyridium.  Body  oblong  or  lanceolate.  Head  continuous  with  the 
body.  Mouth  placed  anteriorly,  subterminal.  Suckers  six,  behind  the  vari- 
olar  margin.  Genital  pores  of  the  body,  ventral,  approximate,  superposed, 
the  larger  in  form  of  a  sucker.  (Diesing.) 

H.  pinguicola,  Treutler.  Body  oblong,  convex  above,  concave  beneath, 
acuminate  anteriorly,  truncated  posteriorly.  Suckers  six  in  number,  ar- 
ranged in  the  form  of  a  semicircle  at  base.  Genital  pores  near  one  another 
in  the  neighborhood  of  the  greater  sucker. 

Measurements. — 8'"  long ;  3'"  wide. 

Habitat. — Ovary  of  human  subject ;  rare. 

H.  venarum,  Treutler.  Body  obtuse,  lanceolate.  Suckers  arranged  in 
two  longitudinal  rows. 

Measurements. — 2-3'"  long;  £-2'"  wide. 

Habitat. — Sputa  of  haemoptysis  and  blood  from  tibial  vein. 

DEVELOPMENT  OP  TREMATODA. 

The  impregnated  egg  of  Fasciola  and  Distoma  hepatica  undergoes  com- 
plete (?)  segmentation.  The  embryo  escapes  as  an  oblong,  ciliated  planula. 
The  subsequent  stages  of  development  have  not  been  traced  in  the  species 
found  in  human  subject,  but  in  other  Trematoda  —  as,  for  example,  the 
species  of  Distoma  infesting  an  aquatic  snail  (Limnceus  stagnates) — the  de- 
velopment has  been  carefully  studied,  and  it  is  reasonable  to  suppose  that  it 
is  not  materially  different  from  that  of  the  other  species.  The  interior  of  the 
planula  produces  independent  larval  forms,  probably  by  a  process  analogous 
to  that  witnessed  in  Aphis.  But  the  larvae,  instead  of  at  once  escaping,  re- 
main within  the  parent  larva  case  (Konig's  gelbliche  Wurm),  as  in  Cecido- 
myia.  This  enclosed  brood,  as  it  may  be  termed,  escaping,  have  evolved  from 
within  their  bodies  a  second  larval  brood  (Cercarice).  Each  zooid  possesses 
peculiar  Distoma-\ikQ  features,  viz.,  two  suckers  and  an  intestinal  tube  bifur- 
cating in  advance  of  a  ventral  sucker,  but  differs  from  Distoma  in  the  pos- 
session of  a  row  of  hooks  about  the  position  of  mouth,  in  the  presence  of  a 
long  natatory  tail,  as  well  as  in  the  absence  of  organs  of  generation.  The 
cercarial  larvae  in  their  turn  escape  from  their  encasement,  and  swimming 
freely  about,  attach  themselves  to  the  integument  of  the  snail  to  be  infested, 
and  endeavor,  by  their  hooks,  to  effect  an  entrance  into  its  tissues.  This 


ENTOZOA.  169 

having  been  accomplished,  the  hooks  and  tail  drop  off,  and  each  larva  passes 
into  the  pupal  afterward  to  assume  the  sexual  form. 

In  Bilharzia  the  eggs  are  of  an  elliptical  shape.  They  develop  minute 
ciliated  planulae.  Their  subsequent  development  has  not  been  investigated. 

CESTODA  (Tapeworms),  Kudolphi.  Composed  of  animals  joined  generally 
for  a  long  time  to  the  nurse  larva — elongate  and  multiarticulate.  Larva 
(head)  furnished  with  two  to  four  pits  or  suctorial  mouths  commonly  armed 
with  hooks;  mature  joints  destitute  of  external  organs,  bringing  forth  em- 
bryos armed  with  booklets ;  alimentary  canal  none. 

Tsenia  (Slender  tapeworm.)  Head  subglobose  or  quadrangular ;  suckers 
four,  rarely  six;  muscular,  orbicular,  opposite,  symmetrical,  strongly  contrac- 
tile. Proboscis  imperforate,  retractile  and  inverted  in  scolex,  but  in  mature 
form  protrusile.  Armed  with  a  simple  double  or  multiple  crown  of  hooks. 
Body  for  the  most  part  plane,  white,  depressed,  bilateral,  or  triangular,  strobile 
articulate.  Mature  segments  hermaphroditic,  separating  successively.  Each 
segment  (called  proglottis)  resembles  a  Trematode.  Water  vascular  system 
transparent.  Genital  pores  lateral,  for  the  most  part  alternate.  Male  pore 
larger  and  anterior,  the  female  smaller  and  posterior.  Genital  organs  per- 
fect. Embryo  small,  active,  and  armed  with  little  hooks;  in  those  which  go 
through  the  '  cysticercus'  form,  oval,  very  small,  ciliated,  yellowish ;  in  other 
larger,  smoother  and  more  transparent.  (Kuchenmeister.) 

T.  solium  (Hooked  tapeworm),  Linn. — Head  about  the  size  of  a  pin-cap, 
globular,  but  produced  in  front  to  form  a  short  conical  proboscis  armed  with 
double  row  of  hooks,  from  twenty  to  twenty-eight  in  each  circular  row;  head 
furnished  with  four  sucking  disks,  and  succeeded  by  a  very  narrow  neck 
nearly  half  an  inch  in  length,  the  latter  being  continued  into  the  anterior 
portion  of  body,  in  which  traces  of  segmentation  at  first  appear  in  the  form 
of  fine  transverse  lines,  which  gradually  becoming  more  and  more  widely  sep- 
arated, leave  brief  interspaces.  The  earliest  formed  joints  are  narrow  ;  the 
proglottides  commence  at  about  the  450th  segment,  the  total  number  of  joints 
in  a  worm  ten  feet  long  being  800.  The  integument  contains  a  number  of 
calcareous  particles  scattered  through  it,  as  well  as  a  small  quantity  of 
chitine. 

A  longitudinal  canal  extends  laterally  along  both  margins  of  individual. 
They  are  in  reality  not  continuous,  but  the  canal  of  each  segment  is  in  a 
degree  complete.  It  pertains  to  a  water  vascular  system.  An  opening  sit- 
uated at  the  side  constitutes  the  sexual  aperture ;  the  orifice  is  very  distinct, 
and  pierces  a  prominent  papilla.  The  pore  is  placed  sometimes  on  one  side, 
sometimes  on  the  other.  In  the  centre  of  the  projection  is  a  small  opening 
in  which  is  found  a  perforate  intromittent  organ  (spiculum),  which  is  in  con- 
nection with  a  tortuous  vas  deferens.  The  testicle  is  placed  toward  the  mid- 
dle of  the  segment.  Behind  the  male  orifice,  and  frequently  confounded  with 
it,  is  the  opening  of  the  female  organs.  The  vagina  passes  parallel  to  the 


170  MEDICAL   ZOOLOGY. 

deferent  canal.  The  ovary  is  a  large  irregularly  lobed  mass  situated  in  the 
centre  of  the  segment.  (Moquin-Tandon.) 

It  is  calculated  that  as  many  as  1200  proglottides  may  be  passed  in  three 
months.  The  Taenia  is  oviparous  ;  each  segment  may  contain  several  hun- 
dred eggs. 

Measurements.— 10'-30'  long ;  4"'  wide. 

Habitat. — Small  intestine  of  man. 

T.  medwcanellata  (Unarmed  tapeworm),  Kuchenmeister.  Head  abruptly 
truncate  at  the  crown,  destitute  of  rostellum,  and  consequently  also  of  a 
hook-apparatus  ;  furnished  with  conspicuously  large  sucking  disks,  usually 
surrounded  by  a  great  quantity  of  dark  pigment  granules  giving  the  head  a 
blackish  appearance.  Ovary  of  the  same  type  as  in  preceding  species,  but 
more  complicated,  presenting  nearly  double  the  number  of  lateral  branches, 
which  do  not,  moreover,  branch  out  so  dendritically.  The  terminal,  360-400 
joints,  may  be  mature.  Joints  apt  to  form  monstrosities,. 

Measurements. — 36'-40'long;  5'"  wide.  (Kiichenmeister.) 

Habitat. — Small  intestine  of  man. 

T.  echinococcus,  Von  Siebold. — Head  with  pointed  proboscis  armed  with 
a  double  row  of  comparatively  large  rooted  hooks  from  thirty  to  forty  in 
number;  the  four  suckers  prominent,  and  succeeded  by  an  elongation  of 
the  segments  forming  the  neck ;  final  segment  when  mature  equalling  in 
length  the  three  anterior  ones  ;  ovary  is  placed  in  median  line  of  proglottis, 
the  oviduct  having  appended  to  it  two  distinct  yolk  glands  modified  near 
its  outlet  into  a  uterine  chamber  and  receptacle.  The  genital  pore  is  at  the 
margin  of  the  proglottis  below  the  central  line.  The  male  organ  consists  of 
numerous  sacs  communicating  with  a  vas  deferens  twisted  upon  itself,  which 
terminates  in  a  constantly  protruded  penis  of  large  size. 

Measurement. — 3'"  long. 

Habitat. — Small  intestine  of  dog  •,  larval  form  (hydatids)  in  man. 

T.  acanthotrms,  Weinland. — Discovered  in  1858.  Cysticercal  form  ;  three 
rows  of  hooks.  Known  only  in  its  larval  form,  which  was  found  in  muscle 
of  man.  (Wyman.) 

T.  flavopuncta,  Weinland. — Proglottis  short,  with  a  'yellowish  spot  clearly 
visible  to  naked  eye,  situated  about  the  middle  of  each  joint.'  Reproductive 
organs  occur  on  one  side  only.  Known  only  from  its  strobile  condition. 

Habitat. — Intestine  of  man, 

T.  nana,  Siebold.  Head  obtuse,  large,  and  placed  on  a  long,  neck-like 
region.  Segments  proportionately  broader  than  in  other  worms.  Eggs 
globular.  Known  from  proglottis-  Obtained  in  considerable  quantities  from 
a  child  who  died  of  meningitis. 

Measurement. — 6'"  long. 

T.  elliptica,  Batsch.  Head  with  conical  proboscis,  armed  with  several 
rows  of  minute  hooks.  An  ovary  or  testicle  upon  either  side  of  each  seg- 
ment, opening  into  a  central  lateral  pore. 

Measurement. — 6-8"  long. 


ENTOZOA.  171 

Habitat. — Intestine  of  cat  and  dog ;  very  rarely  in  man. 

T.  margmata,  Batsch.  Head  subrounded.  depressed,  obtusely  tentra- 
gonal ;  proboscis  short.  Segments  short,  square ;  terminal  ones  oblong. 
Genital  pore  upon  alternate  sides  of  the  segments. 

Measurements. — 1-2^'  long ;  lf-3'"  wide. 

Habitat. — Intestine  of  wolf;  rarely  in  man  (Cobbold)  in  larval  form  (C. 
tenuicollis}. 

T.  lophosoma,  Cobbold.  Strobila  9  feet  long;  breadth  of  each  joint,  £"; 
length  Ty';  proglottides  £  to  f  of  an  inch;  reproductive  papillae  uniserially 
disposed  at  the  margin  on  one  side  throughout  the  entire  colony  of  segments; 
individual  joints  irregularly  pentagonal  in  outline ;  average  diameter  of  the 
eggs,  slo"-  Original  specimen  in  Museum  of  Middlesex  Hospital,  London. 

Bothriocephalus,  Bremser.  Cestodes  furnished  with  two  suctorial  mouths 
or  marginal  oblong,  or  long  opposite  pits.  Head  subquadrangular,  most 
part  articulate.  At  the  centre  of  under  surface  of  each  segment  a  conical 
papilla  emits  the  intromittent  organ.  Behind  this  body  is  another  smaller 
pore  without  a  papilla.  It  is  supposed  to  be  the  vulva,  but  is  not  always 
present.  The  penis  is  furnished  with  a  sheath,  and  communicates  with  a 
tolerably  long  deferent  canal,  which  is  folded  several  times  upon  itself,  grad- 
ually increases  in  thickness,  and  terminates  in  a  vesicula  seminalis,  having 
the  form  of  an  oval  pouch.  The  testicle  consists  of  white  granules,  and  is 
furnished  with  three  slender  ducts,  which  terminate  in  the  above-mentioned 
vesicle.  The  female  organs  are  somewhat  more  complicated ;  the  ovaries 
are  oblong  and  very  distinct ;  the  oviduct  presents  itself  under  the  form  of  a 
tortuous  canal,  especially  at  the  period  when  the  ova  are  mature.  The  uterus 
has  two  pouches  or  diverging  horns.  (Moquin-Tandon.) 

B.  latus,  Bremser  (Broad  tapeworm).  Head  oblong,  unarmed,  two  mar- 
ginal pits  or  fissures.  Neck  inconspicuous.  Joints  about  2000;  mature 
joints  broader  than  long,  separating  in  groups.  Genital  pore  placed  in  me- 
dian line ;  male  opening  larger  and  superior,  from  which  the  broad  and 
smooth  penis  is  prominent.  Quiescent  scolex  unknown. 

Length  2T-24'.  Embryo  with  6  hooks,  in  the  ovule  0'008-32m-  long, 
0-002  broad ;  elliptic  yellowish  brown,  included  in  a  dehiscent  operculura. 
(Kiichenmeister.) 

Habitat. — Intestinal  canal  of  man. 

B.  cordatus,  Leuckart.  Head  heart-shaped,  or  rather  obcordate,  and  set 
on  to  the  body  without  the  intervention  of  a  long  neck.  Segments  increase 
rapidly,  the  anterior  end  becomes  lanceolate:  50  joints  immature;  660 
joints  in  all.  Smaller  than  B.  latus;  calcareous  corpuscles  in  increased  pro- 
portion; 'uterine  rosette'  smaller,  longer,  with  larger  number  of  lateral 
processes. 

Habitat.— Intestine  of  dog  and  man ;  more  frequently  encountered  with 
the  former.  So  far  as  has  been  ascertained,  peculiar  to  Greenland. 


172  MEDICAL   ZOOLOGY. 


DEVELOPMENT    OF    CESTODA. 

Cestode  worms  without  exception  exhibit  alternate  generation. 

The  following  terms  will  be  used  in  its  description  : 

Proglottis. — The  mature  segment,  containing  the  organs  of  generation  and 
the  impregnated  eggs. 

Embryo. — The  first  larval  stage. 

Cysticercus. — The  second  larval  stage.  The  head-like  process  to  Cysti- 
cercus  armed  with  suckers  is  known  as  the  scolex.  It  is  persistent  in  the 
strobilic  form. 

Strobile. — The  segmented  individual.  The  term  is  commonly  applied  to 
the  scolex  and  immature  segments. 

In  T.  solium  the  proglottis  escapes  from  the  strobile  and  is  voided  from 
the  intestine,  the  eggs  soon  afterward  being  discharged  into  the  feces.  In 
this  position  segmentation  of  the  ova  occurs ;  within  each  an  embryo,  having 
a  subrotund  form  and  furnished  at  one  extremity  with  a  circle  of  hooks  re- 
sulting. The  ova  in  this  condition  are  taken  up  by  the  hog  with  its  food 
and  conveyed  into  the  intestine.  Here  the  embryo  escapes,  perforates  the 
intestinal  walls  by  means  of  its  hooks  to  gain  convenient  positions  within 
the  various  muscles  or  viscera  of  the  body.  Favorable  conditions  being 
afforded,  the  second  larval  form,  or  that  of  the  Cysticercus,  is  assumed. 
The  primal  hooks  are  now  lost,  the  larva  being  distinguished  by  the  scolex, 
with  its  suckers  and  peculiar  crown  of  hooks.  In  this  stage  it  becomes  in- 
active, while  the  integumental  covering  becomes  rigid  from  the  presence  of  a 
quantity  of  calcareous  matter.  The  presence  of  large  quantities  of  such  cap- 
sules in  the  flesh  of  the  butchered  hog,  where  they  appear  as  minute  spots 
visible  to  the  naked  eye,  constitutes  '  measly'  pork.  Such  meat,  when  eaten 
raw  or  imperfectly  cooked,  carries  into  the  system  numbers  of  infecting  larvae, 
each  of  which,  when  the  essentials  of  development  are  presented  to  it,  es- 
capes from  its  encasement,  becomes  attached  by  its  hooks  to  the  mucous 
membrane,  and,  losing  its  bladder-like  appendage,  produces,  by  a  process  of 
gemmation,  the  features  characterizing  the  mature  worm.  The  terminal 
segments  in  succession  produce  the  organs  of  generation  in  time  to  be  con- 
verted into  proglottides,  subsequently  to  escape  with  their  eggs. 

In  T.  mediocanellata  the  development  is  the  same,  the  sites  selected 
affording  the  chief  points  of  variance.  The  freed  '  embryo'  is  swallowed  by 
some  ruminating  animal,  as  the  cow,  and  is  received  living  within  the 
alimentary  canal  of  man,  through  the  consumption  of  raw  or  imperfectly 
cooked  beef. 

In  T.  echinococcus  the  larva  is  most  commonly  taken  up  by  the  cow  or 
sheep,  and  the  larval  form  (hydatid)  lodged  within  its  tissues.  The  third 
stage  of  development  is  attained  by  the  dog  devouring  the  infected  beef, 
when  the  mature  form  is  evolved  within  the  alimentary  canal.  Or  the  larva 


ENTOZOA. 


173 


itself  may  be  consumed  by  man  in  his  food  and  water,  and  carried  within 
his  tissues,  very  commonly  to  be  permanently  lodged  within  the  abdom- 
inal cavity  and  brain.  The  mature  form,  in  this  instance,  is  of  course 
never  attained,  unless  through  some  rare  mischance  the  man  be  devoured 
by  the  dog  or  wolf. 

As  may  be  inferred  from  the  above  statements,  the  T.  solium  is  more  com- 
mon with  pork-eaters,  as  the  T.  mediocanellata  is  with  consumers  of  beef. 
Underdone  meats,  or  raw  sausages,  partially  smoked  beef  and  hams  are  pro- 
lific sources  of  disease.  In  the  case  of  T.  echinococcus,  filthy  association 
with  dogs  favors  the  development  of  hydatids.  In  Iceland,  where,  in  addi- 
tion to  such  surroundings  being  very  constantly  present,  the  conditions  are 
exceedingly  favorable  to  increase  of  entozooic  life,  the  ratio  of  occurrence 
of  hydatids  in  the  human  subject  is  perhaps  greater  than  in  any  other  part 
of  the  world.  It  is  calculated  by  Krabbe  that  one  out  of  every  forty,  and 
by  Schleisner  one  out  of  every  seven  inhabitants  harbor  hydatids. 

In  Bothriocephalus  the  scolex  is  formed  as  in  Tcenia,  and  lives  in  the  in- 
testinal canal  of  smaller  aquatic  animals,  in  the  immature  state.  The  strobile 
is  found  within  rapacious  aquatic  animals,  piscivorous  birds  and  mammals. 
Proglottides  very  frequently  separate  in  long  conjoined  series  of  segments. 
Embryos  with  six  hooks.  Coverings  to  ovules  frequently  colored.  (Klichen- 
meister.) 

The  following  table  is  designed  to  show  the  localities  of  the  larval  and 
mature  stages,  as  far  as  known,  of  the  species  of  Taenia  infesting  the  human 
subject. 


T.  solium. 


Strobile  and  ) 


Man. 


Proglottis.  J 
Embryo. —       Earth. 
Cysticercus  {  Hog  (rarely  man). 

(hydatid).   J      (G.  cellulose). 


T.  mediocanellata. 
Man. 
Earth. 
Cow  or  sheep. 


Strobile  and  ) 
Proglottis.  J 


Strobile  and) 


Man. 


Man. 


T.  echinococcus. 
Dog. 

Earth. 

Cow    or    sheep   (comp. 

rarely  man). 
(hydatid). 

Dog. 


T.  acanthotrias. 


TTnknown* 


T.  flavopuncta. 


T.  nana. 


Proglottis.  | 
Embryo.  —      Unknown. 
Cysticercus.  —  Man. 
Strobile  and  )  TT  , 

Proglottis.  j  Unknown. 


T.  elliptica. 


Embryo. —       Unknown. 
Cysticercus. — Unknown. 
Strobile  and  )  -M 
Proglottis.  |  Man' 


Man. 

Unknown. 
Unknown. 

Man. 


T.  marginata. 

Dog  and  wolf. 

Unknown. 

Man  (C.temiicollis). 

Dog  and  wolf. 


Man. 

Unknown. 
Unknown. 

Man. 


T.  lopkosoma. 


Man. 

Unknown. 
Unknown. 

Man. 


174  MEDICAL   ZOOLOGY. 


MOLLUSCA, 

SEPIA  (Cuttle-fish).  Cephalopoda. — Family  Sepiadae. 

Body  oblong,  with  lateral  fins  as  long  as  itself,  shell  as  wide  and  long  as 
body,  very  thick  in-  front,  concave  internally  behind,  terminating  in  a  prom- 
inent point.  (Forbes  and  Hanley.) 


S.  cfficinalis,  D'Orbigny. — Body  large,  ovate,  fleshy,  depressed,  rounded 
behind,  with  a  rounded  projection  on  the  front  of  dorsal  edge,  surface  of  the 
body  smooth.  Fin  narrow,  lateral,  bordering  the  whole  side  of  the  body, 
and  separate  behind.  The  ventral  part  of  the  mantle  furnished  with  an 
oblique  oblong  tubercle  fitting  to  a  concavity  in  the  sides  of  the  lower  part 
of  the  siphuncle.  Head  large,  wider  than  long,  with  two  elongated  and 
some  smaller  beards  above.  Eyes  large,  with  an  inferior  eyelid,  and  a  lach- 
rymal opening  in  the  front  of  the  folds  of  the  eyelid.  Bar  at  the  lower  part 
of  the  globe  of  the  eye.  Buccal  membrane  seven-lobed,  the  two  lower  lobes 
least  marked.  Arms  short,  strong,  unequal ;  order  of  length,  4,  3,  2, 1 ;  ring 
of  cups  smooth,  entire.  Tentacular  arms  much  enlarged,  with  six  alternating 
lines  of  cups,  the  five  central  cups  much  larger ;  ring  of  the  larger  cups 
smoothed,  of  the  smaller  ones  toothed.  Shell  ovate,  compressed,  wrinkled 
above,  semi-cartilaginous  on  the  edge  and  behind,  rounded  posteriorly,  em- 
bedded in  the  back  of  the  animal.  Siphuncle  large,  short,  without  any  band 
at  the  junction  to  the  head,  and  with  a  large  internal  valve.  Back  purple, 
with  darker  cross-bands,  forked,  and  with  small  white  spots  on  the  side. 
(Howe.) 

Measurements. — 8"-9"  long;  6"  wide.  (Forbes  and  Hanley.) 
Habitat. — Atlantic  Ocean,  coasts  of  Europe  and  Africa,  Mediterranean. 


PEOTOZOA, 

INFUSORIA.  Virgulina  tenax. — Body  elongated,  membranous,  transpa- 
rent, somewhat  thickened  at  its  anterior  part ;  it  is  furnished  with  a  tail  one- 
third  or  one-fourth  shorter  than  body. 

Measurement. — T/ffo"  l°nS»' 

Found  in  tartar  of  the  teeth.  (M.  Tandon.) 

Vibrio,  Muller.  Body  filiform,  more  or  less  distinctly  jointed  from  imper- 
fect division  ;  vacuolae  distinct,  globular  hyaline  ;  movement  undulatory. 


PROTOZOA.  175 

Measurements.— -^fay"  to  j^ou"  long  ?  TtToW'  to  TfftfW  wide- 

I7",  rugula. — Found  in  dejections  of  cholera  patients.    V.  bacillus  and  V. 

lineola  are  found  occasionally  in  mucus  of  mouth.     V.  cyanogenus  and  V. 

xanthogenus  at  times  found  in  milk.    V. (?)  has  been  found  in  the  blood 

of  patients  affected  with  malignant  pustule.  (Wood.) 

Paramecium.  Body  covered  with  cilia  ;  no  eyespot ;  a  papilliform  tongue- 
like  process  present ;  aquatic ;  stellate  contractile  vesicle  (q.  v.,  p.  55)  well 
seen.  (Micrograph.  Diet.) 

P.  colt,  Malmstein. — A  species  found  in  the  discharges  of  chronic  dysen- 
tery. Very  rare. 

Cercomonas.  Body  rounded,  or  discoidal,  tuberculated,  with  a  variable 
posterior  prolongation  in  the  form  of  a  tail,  which  is  longer  or  shorter,  and 
more  or  less  filiform.  (Micrograph.  Diet.) 

C.  davainei,  M.  Tandon. — Body  pyriform  ;  integument  soft ;  posterior  pro- 
longation rigid,  straight — serves  to  fix  the  animal  at  times  to  surrounding 
objects.  They  are  true  parasites,  which  live  in  the  intestine  of  man  when  cer- 
tain conditions  are  present  that  are  requisite  for  their  existence.  (Davaine.) 

Measurement. — 3'"  long. 

Rarely  found  in  cholera  dejections. 

C.  oUiqua(1],  Davaine. — Resembles  above,  but  smaller,  more  oval;  cau- 
dal filament  arises  somewhat  from  the  sides.  Rarely  found  in  typhoid 
fever  dejections. 

Trichomonas,  Duj.  Body  ovoid,  or  globular,  becoming  drawn  out  when 
adherent  to  the  slide,  hence  sometimes  exhibiting  a  tail-like  prolongation ; 
an  anterior  flagelliform  filament  present,  with  a  group  or  row  of  vibratile 
cilia. 

T.  vaginalis. — Body  glutinous,  nodular,  unequal,  frequently  becoming  ag- 
glutinated to  other  objects  ;  movement  vacillating.  Found  in  morbid  vaginal 
mucus.  (Mic.Dict.) 

Measurement. — Length  ^ff"- 

PSOROSPERMI^J.— Microscopic,  oval,  depressed,  for  the  most  part  spindle- 
shaped  corpuscles,  with  or  without  a  tail,  exhibiting  no  movements,  and  con- 
sisting of  a  tolerably  firm  outer  coat  covered  with  hair-like  processes  which 
exhibit  a  very  delicate  and  peculiar  structure.  Such  bodies  may  aggregate 
in  cyst-like  masses,  the  contents  of  which  appear  granular  to  low  powers, 
and  exhibit  a  division  into  numerous  segments,  but  it  is  found  to  consist  en- 
tirely of  minute  bodies  resembling  one  another,  possessing  very  definite  char- 
acters, being  oval  flattened,  the  body  slightly  curved  laterally,  with  one 
extremity  blunt  and  the  other  almost  pointed.  Sometimes  they  are  embed- 
ded in  a  ramified  sarcodic  mass.  (Micrograph.  Diet.) 

Measurements, — Corpuscles  t^"  long ;  -5^"  wide.     Diameter  of  cyst 


176  MEDICAL    ZOOLOGY. 

Habitat. — In  fishes,  particularly  upon  the  gills,  in  the  muscles,  and  be- 
tween the  coats  of  the  eye,  in  the  swimming  bladder,  etc.  (Micro.  Diet.) 
In  the  heart  and  voluntary  muscles  of  mammals,  such  as  the  cow  and  sheep, 
they  are  often  numerous.  (Beale.)  They  have  also  been  found  within  the 
muscles  and  viscera  of  the  human  subject.  (Lindeman.) 

Development. — The  entire  mass  increases  in  size  as  the  small  bodies  in- 
crease in  size,  probably  by  division  and  subdivision  within  the  cyst.  (Beale.) 

It  is  believed  by  some  that  there  is  an  intimate  relation  between  these 
bodies  and  the  causation  of  the  cattle  plague  ;*  but  other  observers,  while 
recognizing  the  frequency  of  the  infection  in  animals  dead  of  the  disease, 
attribute  no  power  to  the  Psorospermiae.t  The  significance  of  their  presence 
in  man  has  not  been  ascertained. 

GREGARINID^E,  Dafour.  Round,  oval,  fusiform,  or  cylindrical  bodies,  con- 
sisting of  a  smooth  transparent  cell  wall,  enclosing  a  granular,  more  or  less 
liquid  mass,  with  one  or  more  nuclei  and  nucleoli.  Sometimes  they  exhibit  a 
contraction  in  the  middle,  or  are  divided  by  a  transverse  septum.  In  some  a 
process  resembling  a  head  is  situated  at  one  end,  and  may  be  either  naked 
or  armed  with  hook-like  processes.  Motion  slow  ;  cilia  obscurely  seen  both 
upon  the  outer  and  inner  surface  of  membrane.  One  or  more  long  filaments 
sometimes  arise  from  the  outer  surface. 

Measurements. 

Habitat. 

Development. 

Two  individuals  coming  into  contact  by  corresponding  portions  of  the 
body  become  shortened  and  firmly  united.  A  transparent  capsule  is  next 
formed  around  the  two  individuals,  which  encloses  them  in  a  cyst ;  the  adja- 
cent portions  of  the  cell  membranes  are  absorbed,  and  the  substance  of  the 
two  bodies  become  ultimately  fused.  Globules  or  cells  are  then  formed  in 
the  contents  of  the  cells,  which  subsequently  assuming  the  form  of  the  genus 
Navicula  (boat-like  bodies)  have  been  called  pseudo-naviculae.  These,  the 
young  Gregarinae,  escape  from  the  cell  to  complete  their  development  after 
a  method  unknown.  In  some  cases  it  appears  that  the  contents  of  the 
two  cells  in  conjugation  remain  distinct  until  the  pseudo-naviculae  are 


*  "  In  my  in vestigation  upon  the  muscles  of  animals  destroyed  by  the  cattle  plague, 
I  found  these  bodies  in  enormous  numbers.  While  they  are  ordinarily  found  largely 
in  the  muscular  fibres  of  the  sheep's  heart,  and  to  a  less  extent  in  that  of  the  ox,  they 
are  not  to  be  detected  in  the  best  beef  and  mutton.  On  the  other  hand,  in  almost 
every  specimen  of  cattle  plague  beef  which  I  have  examined,  these  entozoon-like 
bodies  were  present,  and  in  many  cases  in  immense  numbers."  (Beale.) 

f  "  In  the  heart  of  a  healthy  sheep  which  I  afterwards  ate,  I  calculated  there  were 
about  1000  parasites  to  the  ounce,  and  in  the  heart  of  a  healthy  bullock,  which  like- 
wise served  me  for  a  hearty  meal,  the  number  were  rather  in  excess  of  those  in  the 
sheep.  Altogether  at  two  meals  I  could  not  have  swallowed  less  than  18,000  of  these 
psorospermise."  (Cobbold.) 


PROTOZOA.  177 

formed  ;  but  it  is  not  certain  whether  each  single  cell  in  these  instances  has 
not  arisen  from  the  fusion  of  two  others.  (Micro.  Diet.) 


SPONGIA  (Sponge),  Linnaeus.  Sub-class. — Spongidae  characterized  as  fol- 
lows :  Fixed,  aquatic,  polymorphous  animals ;  inhaling  and  imbibing  the 
surrounding  elements  through  numerous  contractile  pores  situated  on  the 
external  surface  ;  conveying  it  through  internal  canals  or  cavities,  and  eject- 
ing it  through  appropriate  orifices ;  having  an  external  flexible  or  inflexible 
skeleton.  (Bowerbank.)* 

Order  Keratosa. 

Spongia  is  distinguished  as  follows :  Skeleton  kerato-fibrous ;  fibre  solid, 
cylindrical,  aspiculous ;  rete  unsymmetrical. 

S.  cfficinalis,  Linnaeus. 


The  Spongice  Ciliatoe  are  held  by  Prof.  H.  J.  Clark  to  belong  to  the  same    • 
family  with  the  Infusoria  Flagellata,  the  connecting  form  being  secured  in  /  I 
the  genera  Codosiga  and  Leucosolenia. 


*  The  other  divisions  of  the  Spongia  are : 

ffalifiaracidse. — Most  elementary  forms,  in  which  a  system  of  water  cavities  has  not 
been  demonstrated. 

ClionidsR,  or  sponges,  which  bore  into  shells  by  means  of  their  siliceous  spicula.  In- 
dications of  their  existence  extend  down  to  the  Silurian  strata. 

Petrospongidss, — A  group  of  organisms  known  only  in  the  fossil  state  and  abound- 
ing in  the  chalk.  They  can  only  be  said  to  be  probably  sponges. 

Tethyidse. — Undoubted  sponges,  but  of  very  hard  texture,  and  furnished  with  very 
long  spicula  which  radiate  from  the  centre  of  each  organism  to  its  circumference. 
(Huxley.) 


12 


ADDITIONS. 


PAGE  12,  paragraph  2.  —  Cilia  present  in  alimentary  canal  of  fishes.  (Stan- 
nius.) 

Page  22,  paragraph  3.  —  Compsognathus,  a  genus  of  Dinosaurian  reptiles; 
possesses  in  the  construction  of  its  posterior  extremities  features  recalling 
those  of  the  birds. 

Page  25,  paragraph  4.  —  Loxosoma,  a  genus  of  naked  Polyzoa.   (Clara- 


Page  30,  second  line  from  top.—  The  V-shaped  bones  placed  below  the 
bodies  of  the  caudal  vertebrae  are  more  properly  recognized  as  "  chevron 
bones." 

Page  37,  paragraph  3.  —  Invertebrata  is  a  term  of  convenience  employed 
in  speaking  of  animals  not  included  within  the  Vertebrata.  It  is  not  consid- 
ered to  have  any  systemic  significance. 

Page  45,  sixth  line  from  top.  —  Paramecium  may  improvise  an  anus. 


I 

(178) 


TABLE  OF  CLASSIFICATION, 


INCLUDING  THE  NAMES  OF  ANIMALS  MENTIONED  IN  THIS  WORK. 


VERTEBEATA. 


Mammalia  (mamma,  the  breast). 

PLACENTALIA  (  placenta,  a  flat 

cake). 
QTJADRUMANA  (qualuor,  four,  ma- 

niLS,  a  hand.) 
Gorilla. 
Semnopithecus. 

CHEIROPTERA    (x^p,    the    hand, 

irrepov,  a  wing). 
Corynorhinus. 
Pteropus. 

INSECTIVORA  (insecta,  insects,  voro, 

to  devour). 
Erinaceus. 
Talpa. 

CARNIVORA  (carnis,  flesh,  voro,  to 

devour). 
Canis. 
Felis. 
Herpestis. 
Lutra. 

Machairodus. 
Phoca. 
Ursus. 
Viverra. 
Vulpes. 

KUMINANTIA*  (ruminare,  to  chew 

the  cud). 
Camelus. 
Cervus. 

Camelopardalis. 
Hyeemoschus. 
Moschus. 
Tragulus. 

OMNIVORA*   (omnis,  all,  voro,  to 
devour). 

Sus. 


PERISSODACTYLA  (nepinaoq,  redun- 

dant, da.K.rv'kog,  a  finger). 
Equus. 
Hyrax. 
Rhinoceros. 

PROBOSCIDIA   (proboscis,  a  trunk, 

fero,  to  carry). 
Elephas. 

KODENTIA  (rodo,  to  gnaw). 
Cavia. 
Castor. 
Lepus. 
Mus. 
Sciurus. 

EDENTATA  (edentuia,  toothless). 
Bradypus. 
Dasypus. 
Manis. 
Myrmecophaga. 

SIRENIA  (oeiprjv,  a  siren). 
Halicore. 

CETACEA  (nfjro^,  a  whale). 
Balsena, 
Catodon. 
Phocsena. 

IMPLACENTALIA  (im,  neg.,  pla- 
centa). 

MARSUPIALIA       (marsupium,      a 

pouch). 
Dasyurus. 
Didelphis. 
Macropus. 
Phascolomys. 


a  hole). 
Echidna. 
Ornithorhynchus. 


*The  orders  Ruminantia  and  Omnivora  are  by  Owen  included  in  a  single 
group,  Artiodactyla  (apnoj,  perfect,  <5a/c™Aoj,  a  finger). 

179 


180 


TABLE    OF    CLASSIFICATION. 


Aves  (avis,  a  bird). 
Anas. 
Anser. 

Archseopteryx. 
Columba. 
Cuculus. 
Cygnus. 
Fringilla. 
Gallus. 
Hirundo. 
Otis. 

Pelicanus. 
Perdix. 
Phasianus. 
Psittacus. 
Rhamphastos. 
Struthio. 

Beptilia  (repto,  to  creep). 

DINOSAURIA     (dslvog,     wonderful, 

ffavpoe,  a  lizard). 
Iguanodon. 
DlCYNODONTIA  (<Mf,  tWO,  KWodovs, 

a  canine  tooth). 
Dicynodon. 

LACERTILIA  (lacerta,  a  lizard). 
Chameleo. 
Amphisbsena. 

CHELONIA  (^e/lww?,  a  tortoise). 

CROCODILIA  (crocodilus,  n.p.). 

Alligator. 

Crocodilia. 
OPHIDIA  (o<f>ic,  a  serpent). 

Ancistrodon. 

Caudisona. 

Cerastes. 

Crotalus. 

Deirodon. 

Hydrophis. 

Naja. 

ICHTHYOPTERYGIA    (l^f,   a   fish, 

TTTepvydc,  a  fin). 
Ichthyosaurus. 

Batrachia  (^drpa^oq,  a  frog). 


Amblystoma. 

Cystignathus. 

Osteocephalus. 

Proteus. 

Bana. 

Salamander. 


Pisces  (pisces,  a  fish). 
PHARYNGOBRANCHIATA 

the  throat,  ppd-y^ta}  gills). 
Amphioxus. 

MARSIPOBRANCHIATA 

bag,  ppd-yx^,  gills). 
Myine. 

ELASMOBRANCHIATA 

plate,  j3pdyx<-a,  gills.) 

SELACHIA  (^e/la^oc,  n.p.  of  Aris- 

totle, cre/laf,  brightness). 
Carcharias. 
Cephaloptera. 
Chimera. 
Lamna. 
Mustela. 
Squalus. 
Squatina. 
Zygeena. 


(from  ray,  n.p.). 
Torpedo. 

GANOIDEI  (yavog,  splendor). 
Acipenser. 
Lepidosiren. 
Lepidosteus. 

perfect, 


TELEOSTEI 

a  bone). 
Anableps. 
Anguilla. 
Aphredoderus. 
Aspredo. 
Blennius. 
Bagrus. 
Compostoma. 
Clupea. 
Cobitis. 
Ditrema. 
Gadus. 
Gymnotus. 
Hippocampus. 
Malapterurus. 
Perca. 
Pimelodus. 
Pleuronectes. 
Salmo. 
Scarus. 
Scomber. 
Tetradon. 
Trichiurus. 


ARTICULATA. 


Insecta,  n.p. 

COLEOPTERA    (/co^eof, 
Ttrepov,  a  wing). 
Calospasta. 
Cysteodemus. 


a    sheath, 


Epicauta. 

Henous. 

Lampyris. 

Lytta. 

Macrobasis. 

Megetra. 


TABLE   OF    CLASSIFICATION. 


181 


Meloe. 

Sarcoptes. 

Mordella. 

Trombidium. 

Nomaspis. 

Thelyphonus. 

Photinus. 

TARDIGRADA. 

Photuris. 
Pleuropompha. 
Potnphopoea. 

Emydium. 

Crustacea  (erusta,  a  shell  or  crust). 

Pyrophorus. 

Cyclops. 

Pyrota. 

Gaminarus. 

Tegrodera. 

Homarus. 

Tetraonyx. 

Lepas. 

HYMENOPTERA  (vfirjv,  a  membrane, 
Ttrepov,  a  wing). 

Lernsea. 
Limulus. 
Lucifer. 

Apis. 
Cynips. 

Lupa. 
Oniscus. 

LEPIDOPTERA  (tenis,  a  scale,  TTTC- 

Palsemon. 

o6v}  a  wing). 

Zoe. 

DIPTERA  (dig,  twice,  Trrepdv,  a  wing). 

Annelida  (annulus,  a  ring). 

Cecidomyia. 

Acoetes. 

Musca. 

Autolytus. 

Pulex. 

Eunice. 

NEUROPTERA  (vevpov,  a  nerve,  Trre- 

Hirudo. 
Lumbricus. 

p6v,  a  wing). 

Nemertes. 

Ephemera. 
Lepisma. 
Libellula. 

Sanguisuga. 
Serpula. 
Terebella. 

Termes. 

Torrea. 

ORTHOPTERA  (bpdtig,  straight,  TTTE- 

Eutozoa  (svroq,  within,  C(5ov,  an 

pov,  a  wing). 
Cicada. 

animal). 

Gryllus. 

NEMATOIDEA  (vyfM,  a  thread,  eldog, 

HEMIPTERA   (ijfit,  half,  Trrepdv,  a 

like). 
Ascaris. 

wing). 

Dracunculus. 

Acanthia. 

Eustrongylus. 

Aphis. 

Gordius. 

Coccus. 

Sclerostoma. 

Nepa. 
Notonecta. 

Strongylus. 
Trichina. 

Pediculus. 
Prionotus. 

Trichocephalus. 

Reduvius. 

TREMATODA(rp^arc5def,  possessing 

holes). 

Myriapoda    (iMpfa,    countless, 

Bilharzia. 

TZOVS,  a  foot). 

Distoma. 

lulus. 

Fasciola. 

Octoglena. 
Scolopendra. 

Arachnida  (Apdypq,  a  spider). 

Hexathyridium. 
Tetrastoma. 

CESTODEA  (KEGTO<;,  a  girdle). 
Bothriocephalus. 

Acarus. 

Tsenia. 

Buthus. 
Demodex. 

Botifera  (rota,  a  wheel,  fero,  to 

Epeira. 

bear). 

Galeodes. 
Gamasus. 

Asplanchnia. 
Melicerta. 

Phrynus. 

Rotifer. 

182 


TABLE    OF    CLASSIFICATION. 


MOLLUSCA. 


Polyzoa  (TToAu?,  many,  CoW,  an  ani- 
mal). 

Plumatella.- 

Brachiopoda  (/fya^'wv,  an  arm, 
TCOVS,  a  foot). 

Crania. 
Lingula. 
Terebratula. 
Waldheimia. 

Tunicata  (tunica,  a  coat). 

Ascidia.  • 
Boltenia. 
Pyrosoma. 
Salpa. 

Lamelliforanchiata  (lamella,  a 
small  plate,  branchiae, 
gills). 

Anodonta. 

Cyclas. 

Mytilus. 

Ostrea. 

Unio. 

Gasteropoda  (rwrfp,  the  belly, 
,  a  foot). 


Aplysia. 

Bulla. 

Chiton. 


Dentalium. 

Doris. 

Eolis. 

Fulgur. 

Helix. 

Janthina. 

Limax. 

Limnsea. 

Natica. 

Nerita. 

Paludina. 

Phyllidia. 

Phyllirhce. 

Strombus. 

Tritonia. 


a  (xrepov,  a  wing, 

a  foot). 
Clio. 
Hyalea. 

Cephalopoda  O^a/ty,  the  head, 
Troii?,  a  foot). 

DlBRANCHIATA  (d't£,  two,  fipayXM, 

gills). 
Argonauta. 
Hectocotylus. 
Sepia. 

TETRABRANCHIATA   (rerpa,   four, 

PpfyXM,  gills). 
Nautilus. 


RADIATA. 


Eehiiiodermata  (^tvo?,  a  spine, 
dlpfia,  the  skin). 

Astropecten. 

Auricularia. 

Bipinnaria. 

Brachiolaria. 

Comatula. 

Echiurus. 

Holothuria. 

Ophiopholis. 

Ophiuris. 

Pe'ntacrinus. 

Pluteus. 

Sipunculus. 

Spatangus. 

Synapta. 

Toxopneustes. 

Ccelenterata  (xono*,  hollow,  &«- 
intestine). 

i,  a  nettle). 


CTENOPHOR^:  («re/f ,  a  comb, 

bearing). 
Beroe. 
Pleurobranchia. 

DlSCOPHOR-E  (cJ^a/cof,  disk,  0opof, 

bearing). 
Aurelia. 
Cyanea. 
Ephyra. 
Geryonia. 
Medusa. 
Physalia. 
Scyphostoma. 

HYDROIDA    (vdpa    [q.v.],    eZJof, 

like). 

Campanella. 
Campanularia. 
Coryne. 
Cordylophora. 
Dicoryne. 
Eucope. 


TABLE    OF    CLASSIFICATION. 


183 


Eucoryne. 

Hvbocodon. 

Hydra. 

Nanomia. 

Perigonimus. 

Ehizogeton. 

Sarsia. 

Syncoryne. 

Tubularia. 


POLYPI 

Actinia. 

Aleyonium. 

Astrangia. 

Gorgonia. 

Isis. 

Laomedea. 


many-footed)  • 


PROTOZOA. 


Infusoria  (infusus,  an  infusion). 

Acineta. 

Bodo. 

Cercomonas. 

Codosiga. 

Dysteria. 

Monaa. 

Paramecium. 

Stentor. 

Stylonchia. 

Trichodes. 

Trichomonas. 

Vibrio. 

Virgulina. 

Vorticella. 


a  root,  TTOV^,  a 


Spongidae,  n.p. 

Leucosolenia. 

Spongia. 

Tethya. 

RMzopoda  (fr 

foot). 

Amoeba. 

Eozoon. 

Noctiluca. 

ITummulus. 

Sphserozoura. 

Thallasicolla. 

Psorospermiae  (</><»f>a,  itch, 
pa,  seed). 

Gregarinidae  (gregarius,  a  flock). 


INDEX  AND  GLOSSARY. 


[n.p.  =  nomen  proprius.'] 


ACANTHIA  (oLKavQa,  a  sting),  151. 

Acarus,  n.p.,  49,  59. 

Achorion,  161. 

Acineta  (dKivrjns,  immovable),  123. 

Acipenser,  n.p.,  37,  42,  70, 116, 145. 

Acoetes  (OKOITTIS,  husband?),  35,  40. 

Actinia  (dm*,  a  ray),  14, 16,  45, 110, 122, 

123. 

Alcyonium  (Myth.,  Alcyone,  the  daugh- 
ter of  ^Eolus),  14. 
Alligator,  43. 

Alytes  (dXvr;7f,  an  executioner),  108. 
Ainoeba  (a/W^  change),  10, 11,  24,  36. 
Amphioxus   (d/*0i?,   on  both  sides,  d%$s, 

sharp),  20,  21,  38,  42,  53,  59,  60,  63, 

76,  98, 116. 
Amphisbsena  (d/*0i,  both  sides,  0aiva,  to 

walk),  50. 
Anableps  (di/^/SXCTw,  to  look  up),  54,  95, 

108, 116. 
Anas,  n.p.,  79. 
Ancistrodon    (dy<c«rrf<jj/,  a    hook,   d<5dj,   a 

tooth),  144. 
Anguilla  (dim.  of  anguis),  n.p.,  64,  70, 71, 

78, 116. 

Anodonta  (dvdfovns,  without  teeth),  129. 
Anoplotherium  (a  priv.,  oir\ov,  defence,  Onp, 

an  animal),  139. 
Anser,  n.p.,  50, 102. 
Ant-eater,  52. 
Aphis,  n.p.,  120, 132.,  153. 
Aphrodederus  (hppudns,  foam,  Sipof,  skin), 

49. 

Apis,  n.p.,  107, 132, 154. 
Aplysia    (a   priv.,  n-Xiiw,  to    wash;   the 

aplysia  of  the  Greek  fishermen  were 

sponges  unfit  for  washing),  39,  46, 

57. 


Apterospasta  (a  priv.,  xrspdv,  a  wing, 
(nroffrof,  a  blister),  148. 

Archseopteryx  (dpx<uoj,  ancient,  irTep6v,  a 
wing),  23,  42. 

Argonauta  (Myth.),  75, 102, 103,107, 113. 

Armadillo,  n.p.,  71. 

Ascaris,  n.p.,  105, 163. 

Ascidia  (dniSov,  a  little  bottle),  69. 

Asplanchnia  (a  priv.,  on\dyx.va,  the  vis- 
cera), 102. 

Aspredo  (asper,  rough),  107. 

Asteracanthion  (forty,  a  star,  axavdiov,  a 
spine),  17,  45,  56,  73. 

Astrangia,  88. 

Aurelia,  n.p.,  14,  68,  92, 120, 126. 

Auricularia  (dim.  of  auris,  ear),  127. 

Autolytus,  131. 

Axolotl,  n.p.,  61, 134. 

BAGEITS,  n.p.,  108. 

Balsena,  n.p.,  41,  81. 

Barnacle,  13,  48. 

Bat,  51. 

Bear,  43, 119. 

Beaver,  44,  71, 119, 139. 

Bedbug,  151. 

Bee,  107, 132. 

Beroe  (Myth.,  the  mother  of  Bacchus), 

26,  45. 

Bilharzia  (Bilharz),  167, 169. 
Bipinnaria  (bis,  double, ^n'wia,  a  leaflet), 

127. 
Blennius  (from  /JXewa,  mucus),  54,  108, 

116. 

Bodo,  n.p.,  10. 
Boltenia  (Bolteri),  69. 
Bothriocephalus  (poQpiov,  a  pit,  *c0aXJ>,  a 

head),  171. 

185 


186 


INDEX   AND    GLOSSAKY. 


Brachiolaria  (Ppaxiw,  an  arm),  127. 
Bradypus  (ffpadis,  slow,  rrovj,  a  foot),  22, 

62. 

Bulla  (bulla,  a  bubble),  39,  93. 
Bustard,  50. 
Buthus  (/foifr ,  a  bull,  fods,  swift),  48. 

CALOSPASTA  («aXdf,  beauty,  (nracrroy,  a  blis- 
ter), 149. 
Camelopardalis  (camelo,  camel,  pardalis, 

leopard), 

Camelus,  n.p.,  102. 
Campanella  (dim.  of  campana,  a  bell), 

126. 

Campanularia  (ibid.),  124. 
Campostoma   (/ra^rdf,   flexible,  <rrfyia,  a 

mouth),  49,  60. 
Canary,  79. 
Canis,  n.p.,  103, 119. 
Cantharis,  n.p.,  147. 
Carcharias  (icdpxapos,  sharp-pointed),  133. 
Castor,  n.p.,  44,  71,  92, 119, 139. 
Cat,  43. 
Caudisona  (cauda,  tail,  sona,  to  Bound), 

87, 143. 

Cavia,  n.p.,  119. 
Cecidomyia  (tcfiKifos,  an  excrescence,  i*via, 

a  fly),  120, 132. 
Cephaloptera  (*f<£aX>7,  head,  nrepdv,  wing), 

95. 

Cerastes,  n.p.,  144. 
Cercaria  (nipm;,  a  tail),  168. 
Cercomonas  (xipKos,  a  tail, /toyfe,  a  monad), 

175. 

Cervus,  n.p.,  103, 138. 
Chameleo,  50. 
Chimera,  89. 
Chiton,  57. 

Cicada,  n.p.,  102, 131. 
Civet,  119, 139. 
Cleopatra's  asp,  144. 
Clio,  47, 112. 
Clupea  (Pliny's  name  for  a  small  fish), 

116. 

Cobitis,  54. 
Cobra  di  capello,  144. 
Coccus,  n.p.,  153. 
Cod,  50, 145. 
Columba,  n.p.,  50. 

Comatula  (coma,  a  bunch  of  hair),  17. 
Cony,  52, 141. 


Copperhead,  144. 

Cordylophora  (Kop6v\n,  a  club,  <pop6s,  to 
bear),  124, 125. 

Coryne  (mtfvq,  a  club),  120, 124, 126. 

Corynorhinus  (Kopvvn,  a  club,  piv,  a  snout), 
101. 

Crab,  14, 122. 

Crania  (cranium),  128. 

Cricket,  102. 

Crocodile,  102. 

Crocodilia,  n.p.,  91. 

Cuckoo,  51. 

Cuculus,  n.p.,  51. 

Cyanea  (xvaveos,  dark  blue),  88. 

Cyclas  (KVK\CLS,  orbicular),  111. 

Cyclops  (KwcXwi//,  cyclops,  literally,  round- 
eyed),  58, 107. 

Cygnus,  n.p.,  50. 

Cynips,  n.p.,  107, 155. 

Cysteodemus  (/cwmj,  a  bladder,  MH<IS,  a 
body),  147. 

Cystignathus  (*wm?,  a  bladder,  yvaQos,  the 
jaw),  102. 

DAMAN,  119, 141. 

Daphnia,  n.p.>  48,  94. 

Dasypus  (<5aovy,  hairy,  novs,  a  foot),  35, 71. 

Dasyurus  (<5a<n5j,  hairy,  ovpa,  tail),  81. 

Deer,  103. 

Deirodon,  42. 

Demodex  (<5cftaf,  the  body,  <5f)£,  a  worm), 

158. 

Dentalium  (dens,  a  tooth),  22. 
Dicoryne  (Sis,  two,  Kopvvr},  a  club),  126. 
Dictylium,  153. 
Dicynodon  (&j,  two,  Kwo5ov$,  canine  tooth), 

43. 
Didelphis  (Sis,  two,  fcX^Oj,  a  womb),  118, 

119. 

Distoma  (Sis,  two,  orfyta,  mouth),  166, 168. 
Ditrema  (Sis,  two,  rpfyo,  a  foramen),  108. 
Dog,  103, 119. 
Dogfish,  50. 
Dolphin,  119. 

Doris  (Myth.),  24,47,  51,  57,  74, 107, 129. 
Dracunculus  (dim.  of  draco,  a  dragon), 

164. 

Dragon-fly,  115. 
Duck-bill,  41,  80, 100,  118. 
Dugong,  62. 
Dysteria  (Dyster),  39. 


INDEX   AND    GLOSSARY. 


187 


EARTHWORM,  113, 122. 

Echidna  (e\tSva,  a  viper),  100, 180. 

Echiurus   (ex's,  a  viper,  oi>f>a,  tail),  22, 

56. 

Eel,  64,  70,  71,  78, 116. 
Electric  eel,  49. 
Elephant,  38,  52,  80,  92,  119. 
Elephas,  n.p.,  38,  52,  80,  92,  119. 
Eolis  (Myth.),  4,  129. 
Eozoon  (i?wf,  the  dawn,  £woi/,  an  animal), 

24. 
Epeira    («rrifo/ioi,    I    examine),    48,    59, 

104. 

Ephemera,  59. 
Ephryra  (Myth.),  126. 
Emydium  (EUU?,  a  turtle),  59. 
Epicauta  (im,  upon,  KO.VW,  tail),  149. 
Equus  (equus,  n.p.),  43,  51,  52. 
Erinaceus,  n.p.,  119. 
Eucope,  120,  124,  125,  126. 
Eucoryne  (ev,  beautiful,  xopuvri,  club),  88. 
Eunice  (Myth.,  daughter  of  Nereus  and 

Doris),  58. 
Eustrongylus    (ev,  beautiful,    orpoyyOXo?, 

rounded),  165. 

FASCIOLA  (dim.  of  fascia),  165, 168. 

Felis,  n.p.,  43. 

Fiber,  n.,  119. 

Flounder,  116. 

Fowl,  37,  62. 

Fox,  80. 

Fresh- water  shrimp,  14. 

Fringilla,  n.p.,  79. 

Frog,  42,  53,  54,  61,  64,  71,  76,  78,  99, 103, 

117,  134. 
Fulgora  (fulgeo,  to  shine),  107. 

G-ADUS,  n.p.,  50,  78, 145. 

Galeodes  (yaXcw^?,  weasel-like),  48. 

Gall-fly,  107. 

Gallus,  n.p.,  37,  62, 102, 118. 

Gamasus,  n.p.,  49. 

Gammarus,  n.p.,  14. 

Gar,  61. 

Geryonia,  Myth.,  97. 

Gillaroo  trout,  49. 

Giraffe,  52. 

Gnathium  (yvaSoj,  jaw),  148. 

Goose,  79. 

Gordius,  Myth.,  107. 


Gorgonia  (Myth.,  a  daughter  of  Phorcys, 
whose  locks  were  changed  into  ser- 
pents by  Minerva),  35. 

Gorilla,  n.p.,  119. 

Gryllus,  102. 

Guinea-pig,  119. 

Gymnotus  (yu//^,  naked,  vwroy,  back),  83. 


HADDOCK,  78. 

Halicore  (SX?,  sea,  K<5p/7,  a  maid),  62. 
Hammer-headed  shark,  50. 
Hectocotylus  (tKarov,  a  hundred,  Korv\rj,  a 

sucker),  113. 
Hedgehog,  119. 
Helix  (eXif,  a  spiral),  23,  46,  47,  66,  104, 

106,  112,  122. 
Henous,  147. 

Herpestis  (ip™,  I  creep),  119. 
Herring,  116. 
Hessian  fly,  120,  132. 
Hexathyridium  (?£,  six,  Qvpifiiov,  a  little 

door),  168. 
Hippocampus    ("TOO?,  a    horse,  KU^TI,  a 

bending),  60,  108. 
Hirudo,  n.p.,  48,  58,  159. 
Hirundo,  62. 
Holothuria  ('o\o9ovpm,  sea-  tail),  17,  22,  46, 

55,56,104,110,  111,122. 
Homarus,  n.p.,  48,  58,  75,  94,  97,  104,  107, 

114. 

Horse,  43,  51,  52. 

Hysemoschus  (i>?,  hog,  /*<5<r*of),  n.p.,  139. 
Hyalea  (Myth.,  Hyale,  a  nymph  in  the 

train  of  Diana),  39. 
Hybocodon  (t>/?of,  a  hump),  126. 
Hydra  (Myth.,  vfya,  a  fabled   monster 

with   many  heads),  14,  38,  45,  88, 

101,  110,  120,  122,  123,  124. 
Hydrophis  (Wwp,  water,  <50<j,  a  serpent), 

145. 

Hylodes  (tfX&xfo,  sylvaticus),  108. 
Hyrax  (fyofc  a  rat),  52,  119,  141. 

ICHTHYOSAURUS    (iKdijf,    a    fish,  erat/pof,   a 

lizard),  95. 
Iguanodon  (Iguana,  a  genus  of  Saurian 

reptiles,  d<5ot>?,  tooth),  43. 
Isis  (Myth.,  an  ancient  goddess),  35. 

JANTHINA  (lavQivog,  violet),  93,  107. 
Julus,  n.p.,  104. 


188 


INDEX    AND    GLOSSARY. 


KANGAROO,  51, 118,  119. 
King-crab,  41. 

LABYRINTHODOJST  (\af3vpivdo;,  a  labyrinth, 

Atafc,  a  tooth),  23;  42,  71. 
Lamna,  n.p.,  63. 
Lampyris,  n.p.,  87. 
Lancelet,  42,  59,  76. 
Laomedea  (Myth.,  one  of  the  Nereids), 

104, 124. 
Lernsea,  58. 

Lepas  (Xbras,  a  small  dish),  13,  48,  58. 
Lepidosiren,  23,  76. 
Lepidosteus  (Am's,  a  scale,  tortou,  bone), 

35,  61. 

Lepisma  (Awf?,  a  scale),  131. 
Lepus,  n.p.,  100. 

Libellula  (dim.  Kbella),  n.p.,  95, 115. 
Limax,  n.p.,  66. 

Limnceus  (Ai/ivaib?,  marshy),  46,  47. 
Limulus  (dim.  of  limus,  sideways),  41, 

48. 

Lingula  (lingua,  n.p.,  dim.),  46. 
Loach,  54. 

Lobster,  75,  94, 104,  107, 114. 
Locust,  102,  131. 
Louse,  127, 131. 

Lucifer  (lux,  light,  fe.ro,  to  bear),  97. 
Lumbricus,  n.p.,  48,  58,  113,  122. 
Lupa,  n.p.,  14,  122. 
Lutra,  n.p.,  101,  119. 
Lytta,  n.p.,  149. 

MACHAIRODUS   (//dxatpa,  a  sabre,  6tov;,  a 

tooth),  43. 
Macrobasis  (/io<cpof,  long,  /?<*<T<?,  a  base), 

148. 
Macropus  (fiavpoV,  great,  MS,  a  foot),  51, 

118,  119. 
Malapterurus  (//aAoj,  soft,  nrepov,  a  wing, 

oiipa,  tail),  84. 

Manis  (manus,  the  hand),  42,  71. 
May-fly,  59. 
Medusa,  n.p.,  97, 124. 
Megetra  (/^ya?,  great),  147. 
Melicerta,  n.p.,  47, 
Meloe,  n.p.,  147. 
Mite,  59. 
Mole,  95, 101. 
Monad  (novas,  a  unit,  a  minute  proto- 

zoon),  9. 


Mordella  (mordeo,  I  bite),  95. 

Moschus,  n.p.,  137. 

Mud-fish,  61,  76. 

Musca,  n.p.,  94, 131. 

Musk-rat,  117. 

Mus,  n.p.,  102, 103. 

Mussel,  74,  103,  104,  107. 

Mustela,  n.p.,  50. 

Myrmecophaga  (^vp^-rixos,  an  ant,  0ay«, 

to  eat),  42,  52. 
Mytilus,  n.p.,  74. 
Myxine  (//i5£u/o?,  slime-fish),  98. 

NAJA,  n.p.,  144. 

Nanomia,  n.p.,  124. 

Natica,  n.p.,  93. 

Nautilus  (vcrorfAo?,  nautilus),  47,  58,  75, 

87,  93. 

Nemertes  (ny/tcpr^,  unerring),  n.p.,  38,  75. 
Nemognathus  (">?/«*,  a  thread,  yyufo?,  jaw), 

148. 

Nepa,  n.p.,  104, 153. 
Nerita  (vripsirris,  a  sea-shell),  38. 
Noctiluca  (nox,  night,  luceo,  I  shine), 

86. 
Nomaspis    (vfyto;    law,  amis,  a    shield), 

147. 
Notonecta    (vwroj,    the    back,    MWCTO,    to 

swim),  152. 
Nummulus  (nummus,  a  coin),  24. 

OCTOGLENA   (OKTO),  eight,  y^vrj,  eyeball), 

40. 

(Ethalium,  11. 
Oidium  (oj&w,  to  swell),  161. 
Oniscus,  n.p.,  104. 
Ophiopholis  (tyig,  a  snake,  $0X1$,  a  scale), 

17. 

Ophiura,  45,  56,  122. 
Opossum,  118, 119. 

Opuntia  ( Opus,  a  city  of  Locris),  154. 
Oreodon  (opoj,  a  mountain,  <5<5oi5j,  a  tooth), 

139. 
Ornithorhynchus    (tpvis,   a   bird,  jtiyws, 

snout),  23,  41, 100, 102, 110. 
Osteocephalus  (orrtov,  a  bone,  Ke<pa\)i,  the 

head),  108. 

Ostrea,  n.p.,  46,  57,  69,  74,  111. 
Ostrich,  37, 118. 
Otis,  n.p., -50. 
Otter,  101, 119. 


INDEX   AND    GLOSSARY. 


189 


Oxyuris  (<>&,  sharp,  oi>pa,  tail),  39,  163. 
Oyster,  74,  111. 

PAL^EMON  (Myth.,  Palsemon,  a  sea-god), 

97. 
Paludina    (dim.    Palus],    54,    57,    108, 

112. 

Pangolin,  42,  71. 
Paramecium  (Trapa^/c^?,  oblong),  45,  55, 

110,  122,  175. 
Parrot-fish,  42. 
Partridge,  37. 

Pediculus  (pediculus,  a  louse),  131, 156. 
Pelicanus,  n.p.,  50. 

Penicillium  (penicillum,  a  pencil),  161. 
Pentacrinus  (Twruj,  five,  Kpivov,  a  lily), 

35,  46. 

Perca,  n.p.,  63,  116. 
Perch,  63, 114,  116. 
Perdix,  n.p.,  37. 
Perigonimus  (mpi,  around,  yovrj,  a  seed), 


Porcupine  ant-eater,  80. 

Porpoise,  51. 

Prionotus    (irpiuv,  a    saw,    V&TVS,   back), 

152. 
Proteus    (Myth.,    a    sea-deity,   son    of 

Oceanus  and  Tethys),  53,  61,  91,  99, 

117,  122. 

Protococcus  (jr/xjrof,  in  front),  11. 
Psittacus,  n.p.,  62. 

Pteropus  (irtEpov,  a  wing,  TOUJ,  a  foot),  51. 
Pulex,  n.p.,  156. 
Pyrethrum,  n.p.,  157. 
Pyrophorus  (nvp,  fire,  <popds,  that  which 

bears),  87. 
Pyrosoma    (nvp,    fire,    a&na,   the   body), 

128. 
Pyrota,  n.p.,  149. 


RANA,  n.p.,  42,  53,  54,  61,  64,  71,  76,  78, 

99,  103, 117,  134. 
Rat,  103. 


125.  Rattlesnake,  142. 

Phascolomys  (</>a<moXdj,   a  pouch,  //%,  a    Reduvius,  n.p.,  152. 


mouse),  51,  52,  81. 
Phasianus,  n.p.,  37. 
Pheasant,  37. 

Phoca  (0'^nj,  a  seal),  35,  62,  95,  101. 
Phocsena,  n.p.,  51,  68,  119. 
Phodaga  (Q-ofes,  pustules,  ayw,  to  cause). 
Photinus  (0wT«i^s,  shining),  87,  102. 
Photuris  (<£w?,  light,  ovpa,  tail),  87. 
Phrynus  ($pvws,  a  toad),  40,  89. 
Phthirius  (<j>Qdp,  a  louse). 
Phyilidia  (0»AXfc,  a  leaf),  57. 
Phyllirhce  (<j>v\\is,  a  leaf,  par,,  the  wave), 

112. 

Physalia  (<ptaa,  a  bladder),  24,  45,  88. 
Pillbug,  104. 

Pimelodus  (mneXofo,  fat),  n.p.,  35. 
Plant-louse,  132. 
Pleuronectes  (-nXwpnv,  the  side, 

swim),  116. 
Pleurobranchia  (nXsvpov,  a  lung, 

gills),  45. 
Pleuropompha    (it\evpaf  a    rib, 

blister),  149. 
Plumatella  (dim.  of  plumata,  feathered), 

106. 

Pluteus,  127. 
Pomphopoea   (TTO 

make),  149. 


to 


OJ,  a  blister,  mieu,   to 


Rhamphastos  (p'l^o;,  a  sharp  snout),  62. 
Rhinoceros  (ptv,  p«foj,  the  nose,  xipas,  a 

horn),  38,  52,  68,  72. 
Rhizogeton  (/J«£a,  a  root),  110, 125. 
Rotifer  (rota,  a  wheel,/ero,  to  carry),  47. 

SABRE-TOOTHED  TIGER,  43. 

Salamander,  103. 

Salmo,  n.p.,  37,  49,  78,  116. 

Salmon,  37. 

Salpa  (ffiXim,  stock-fish),  37,  69,  86,  108, 

111,  128. 
Sanguisuga  (sanguis,  blood,  sugo,  to  suck), 

48. 

Sarcina  (aapl,  flesh),  161. 
Sarcoptes  (aap%,  flesh,  KOKTW,  to  cut),  157. 
Sarsia  (Sars),  126. 
Scarus,  n.p.,  42. 
Sciurus,  n.p.,  103. 
Sclerostoma  (oxMpd?,  rigid,  ord//a,  mouth), 

164. 

Scolopendra,  n.p.,  82,  83,  87,  159. 
Scomber,  n.p.,  60. 
Scorpion,  48. 
Scyphostoma  (awtpos,  a  drinking-bowl), 

126. 

Sea-anemone,  16. 
Sea-cucumber,  46. 


190 


INDEX   AND    GLOSSARY. 


Sea-hare,  57. 

Sea-lily,  46. 

Sea-urchin,  45,  110,  111. 

Seal,  35,  62,  95, 101,  119. 

Semnopithecus  (at^os,  venerable,  TTJ^KOJ, 
monkey),  51. 

Sepia,  58,  87,  93,  106, 107. 

Serpula  (serpo,  to  creep),  48,  58. 

Shark,  57, 102, 108. 

Silver-moth,  131. 

Sipunculus  (siphunculus,  a  little  water- 
ing-pot), 22. 

Sloth,  22,  62. 

Snail,  23,  46,  47, 104. 

Spatangus,  n.p.,  46. 

Sphserozoum  (odaipa,  a  globe,  ^ov,  an 
animal),  24. 

Spongia,  177. 

Squalua,  n.p.,  37,  76,  78,  102,  108. 

Squatina  (dim.  of  squatus,  a  skate),  63. 

Squirrel,  103. 

Starfish,  45,  73. 

Stentor,  n.p.,  104,  122. 

Strombus,  n.p.,  93. 

Strongylus  (arpoyyvAof,  rounded),  162. 

Struthio,  n.p.,  37,  118. 

Sturgeon,  37,  42,  70,  116. 

Stylonychia,  122. 

Sus,  92. 

Swallow,  62. 

Swan,  50. 

Syncoryne  (aw,  with,  Kopvvr),  a  club),  92. 

Synopta  (avixmros,  conspicuous),  45,  110, 
111. 

T^NIA  (raivia],  12,  107,  169. 

Talpa,  n.p.,  87,  95, 101. 

Tardigrada  (tardus,  slow,gradus,  a  step), 

115. 

Tegrodera,  149. 

Terebella  (terebra,  an  auger),  24. 
Terebratula  (terebra,  an  auger),  46. 
Termes,  n.p.,  102. 
Tethya    (Myth.,    daughter    of   Uranus 

and  Terrus),  109,  110,  123. 
Tetraodon  (rerpa,  four,  dcfcwy,  tooth),  85. 


Tetraonyx  (rerpa,   four,  5™$,   nail,   Me- 

loides),  149. 
Tetrastoma  (rerpa,  four,  crfyta,  a  mouth), 

168. 
Thallasicolla  (Qa\aaaa,  the  sea,  <coAAao>,  to 

join  together),  24. 
Thelyphonus   (dijXvs,  a  woman,  0dw>j,  a 

homicide),  40,  89. 
Torpedo,  n.p.,  82. 
Torrea,  94,  97. 
Toucan,  62. 
ToxopneusteS  (r<5£o»/,    a    bow,   irvsvarda},   to 

breathe),  17,  35)  39,  45,  46,  110,  111. 
Tragulus  (dim.  of  tragus),  138. 
Trichina  (rpixtvof,  made  of  hair),  161, 
Trichiurus  (0pi£,  hair,  oi>pa,  the  tail),  85. 
Trichocephalus   (0pi£,   hair,    KtyaXii,   the 

head),  162. 

Trichodes  (0pif,  hair),  123. 
Trichomonas  (Qpi$,  rpi'^dj,  a  hair,  monos], 

45, 175. 

Tritonia  (triton,  a  weather-cock),  39. 
Trombidium  (rpo/z/?o><3of,  timid),  49. 
Tubularia  (tubulus,  a  little  pipe),  125. 

UNIO  (unio,  a  pearl),  38,  74, 103, 107. 
Ursus,  n.p.,  43, 119. 

VIBRIO  (vibrio,  I  shake),  9, 174. 
Vipera,  n.p.,  144. 
Virgulina,  174. 
Viverra,  n.p.,  119,  139, 
Volvox  (voltere,  to  turn),  12. 
Vorticella  (vortex,  a  whirlpool),  38, 122, 

123. 
Vulpes,  n.p.,  80. 

WALDHEIMIA  ( Waldheim),  46. 
Water-bear,  59. 
"Water-moccasin,  144. 
Whalebone  whale,  41,  81. 
Wombat,  51,  52,  81. 

ZOE  (^,  life),  131. 

Zonitis  (faiHrij,  a  zone),  148. 

Zygeena, 


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